What Should I Know About Changing The NSX's Engine Oil?

No special tool is needed for an oil-change; however, make sure you use a new crush washer in and apply the right torque. The manual specifies 33lb-ft of torque on the oil pan drain plug and 16 lb-ft (one turn) on the oil filter (after applying oil to the  rubber seal and using a NEW crush washer - reusing the crush washer will mess up this torque reading).


What Kind Of Engine Oil Should I Use?

Stick to the factory manual recommendations for viscosity: 10W-30 for most conditions, 5W-30 if the ambient temperature is regularly below freezing when the car is in operation.

Always change the filter when you change the oil. Use the OEM Honda filter designed the NSX only. Other filters will fit but the Honda filter for the NSX is superior in quality and filtering ability.

Many NSX owners prefer to use a synthetic engine oil. Synthetics have better flow at startup and more resistance to breakdown under severe operating conditions such as high temperature.

However, the fact is that the frequency of oil changes is more important than the type of oil for most cars. The manual recommends changing the oil ever 3750 miles under "severe" conditions. Most cars are driven under "severe" conditions - in the case of the NSX that means either driven hard (like a sports car) or driven infrequently with lots of stop-and-go traffic.

A car that is not driven on the track will be just fine using regular motor oil every 3000 miles. For those who want a little extra protection when they drive their car hard or who drive their car at the track, synthetic is probably a good idea. Many people change their oil after a track event, and sometimes before as well depending how long it has been since they last changed it.

Among synthetics,  Redline is one of the most expensive (~$8/qt). Some racers swear by it, but it is certainly overkill for cars that are not on the track all the time. Note that Redline's single-weight RACE oils do not have the detergents you need for street use. Do NOT use Redline RACE oil unless you have a dedicated race car and change  the oil after every day at the track. Their multi-viscosity street oils are fine for normal use.

For street and moderate track use, Mobil 1 seems to be the most popular and is less expensive ($3-$5/qt depending where you buy it).


I Heard Synthetic Oil Caused Engine Failure In Airplanes..?

These stories and rumors are based around Mobil AV-1, Mobil's attempt at marketing a synthetic aviation oil in the early '90s. This has no relation to the Mobil 1 synthetic oil for automobiles.

It was mostly the larger, high displacement (and higher blow-by) engines were having problems with AV-1. Mobil eventually owned up to the top-end damage (sludge buildup, piston ring malfunction and piston blow-by resulting in cylinder/piston damage and high oil consumption.) But they denied the bottom-end damage many people claimed were caused by AV-1 (camshaft lobes, crankshaft/connecting rod bearings and counterweight dampers) even though the FAA said they were sufficiently documented (FAR 21.3). These problems typically took 250-500 hours to occur.

AV-1 went off the market after a few years. The FAA rescinded Mobil's STC for AV-1 in May 1996, which was announced in the FAA General Aviation Airworthiness Alerts (AC 43-16).

There was a settlement for a class action lawsuit for people who'd used AV-1 on Continental engines over 360 ci. This left a lot of people out.. For example, TIO-540 Lycomings fared as poorly with AV-1 as TSIO-520 Continentals.

"TBO Advisor" covered this whole ordeal as it came to a head (around 1994-1996) pretty extensively because Kas Thomas was personally PO'd about the whole matter.


Which Oil Filter Should I Use?

Acura/Honda OEM Filter

[KS] Most dealers will be happy to give you a nice discount if you buy a box (half a dozen, I think) of oil filters at a  time. Not only is this a good deal, but it's also useful if you want to go back to the same dealer for the oil changes - they won't charge you for the filter each time but they won't resent it the way they might if you bought them elsewhere

When you're buying the filters, don't forget to buy the washer that you'll need for installing each filter. It's a good idea to tape one washer to the cellophane wrapper on each filter - that way you won't lose them and you'll have them handy.

The oil filters for the 1990 Legend and the NSX were the same. Then, Acura changed the Legend oil filter to a smaller size. As I recall this was around June of 1995. The price of the NSX oil filter also increased in price, while the "new" Legend filter decreased in price. 15400-PL2-004 is the part number for the NSX filter.

[JJN] I paid about $8 per filter for mine from Worldwide Auto Parts (who is unfortunately out of business - now I know why) but here are a couple of others:

Hoehn Acura: 800-984-6346 - $11.37 per filter
A&H Motorsport: 800 543-5525 - $11.43 per filter

Back of any car mag has others if you want to shop around some more.


[RWI] I used Fram once with disasterous results. About 4 years ago, I decided to change my oil one Sunday. Unfortunately, no Acura dealers were opened on Sunday. So, I ran to my local Pep Boys and puchased myself an equivalent Fram filter. Did my oil and filter change as usual and went for a test drive. After about 20 mins driving around, I decided to take it to about 100 mph. Guess what, my oil presure dropped to zero and one of the idiot lights started blinking.

I immediately shut the engine off and assesed what had happen. There was smoke coming from the rear right side of the car but not on the left. Believe me, it was a scary experience. I was almost in tears while I pulled off the side of the road. I got out of the car and saw a trail of oil on the road leading up to my car. I remember praying as I carefully peeped under the car. First thing I noticed was the car's left underside was very clean. I decided to jack up the car right there and then so I could see more underneath. Further examination revealed the Fram rubber seal burst spilling most of the oil out of my engine.

I told myself then, I will never ever use a non-factory filter my my NSX again. The next day, I took my car to the dealer and had them checked everything in my engine. Fortunately, the dealer said the engine has no detectable damage. It took at least 3 under carriage steam cleaning before I got all the oil out of the little crevices under the car. The moral of the story, don't skimp on oil filters, use the oil filter specifically designed for you car.

[DNG] Fram oil filters are know for this. Frams were banned from being used on race bikes since they kept blowing. I'd rather spend $4 more for piece of mind with the OEMs.


What About Oil Additives?

Do not use oil additives! You do not need them, they provide no real-world benefit, and in some cases can actually cause damage to your engine.


In the October issue of Consumer Reports they made a note about "Prolong engine treatment".

(This is directly from the article)

Prolong claims: "Creates a low-friction surface one molecule thick"

The bond is supposed to last even when the oil is drained. In the infomercial, Unser and others drive along a racetrack in the Mojave Desert without oil or oil drain plugs. The same ad, broadcast nationally, pictures a woman who, thanks to "Prolong" supposedly drove from Santa Barbara to Los Angeles without oil. (the reason she stopped after 4 hours,40 minutes, and 7 seconds? ..She was hungry.)

We didn't test the other claims, but we did see whether "Prolong" would protect an engine after the oil was drained.

We installed a factory-rebuilt GM 4.3-liter V6 engine into each of two Chevrolet Caprices. We broke them in with Pennzoil motor oil, changed the oil and oil filter in each car, and added "Prolong" to one of them. "Prolong" claims to work immediately. We drove more than 100 miles, then drained the oil and started driving again. After only 13 minutes and five miles, BOTH engines failed SIMULTANEOUSLY.

Today's high-quality oils don't need extra additives. The Federal Trade Commission has told the makers of other additives to stop making false claims. We have notified the FTC about this test.


Oil Analysis

As anyone who owns an aircraft already knows, oil analysis is an extremely valuable tool. 

One of the best known oil analysis companies is called Titan Laboratories. They provide quick turnaround, keep detailed records on each of the cars you send samples from so you have historical data comparison, perform both wear metal analysis and physical/chemical tests of the oil itself, and typically telephone you immediately if during testing they discover something drastically wrong with a sample. They provide all the sample-taking hardware, sample bottles, and self-addressed boxes.

Titan Laboratories
1380 Zuni Street
P.O. Box 40567
Denver, Colorado 80204
Phone 1-800-848-4826
Fax 303-595-8741

[KJ] I ran Castrol Syntec for about 7500 miles. I sent a sample to a lab for analysis, and it came back fine. The results were as follows:

Wear Metals

My Sample (ppm)

"Typical" according
to the lab (ppm)























My Sample (ppm)

"Typical" according
to the lab (ppm)

























Also, the oil was still partly transparent, not totally black as it would be on a normal car. The oil level drop was less than 0.3 quarts, some of which may be due to a lower ambient temperature in December than in June. This is one amazing engine! Next time I'm changing it at 5000 miles max, just to show proper respect for the engine.

[GM - 99/2/5] I've used a company called SmartCheck for years. They give you a readout that tracks all sorts of contaminants. They have a legend that tells you what the different contaminants in the oil indicate about the state of your engine. Due (I guess) to the fact that I use top quality oil and change it every 3-5000 miles I've never seen a spike that would indicate the need for an oil change. They measure Iron, Chromium, Lead, Copper, Tin, Aluminum, Nickel Silver and Manganese as wear elements, and Silicon, Boron, Sodium and Glycol as contaminants.

18419 Euclid Avenue
Cleveland OH 44112-1016


What Transaxle Oil Should I Use?

[RM, KJ, [email protected]] As with engine oil, Redline is again the favorite for those not primarily concerned with cost. When buying Redline transmission oil for their NSX, many people are unsure if they should get MT-90 or MTL. The only difference is weight; MT-90 is based on a 40-weight synthetic, MTL on a 30-weight. You can use either, but in general those in colder climates will do better with MTL and those in warmer climates with MT-90.

Most folks who have complained that their shifts were not as smooth have been using MTL.

[MJ] I put Redline MTL in there, @ $9.00/quart and it was "notchy" before and it is "notchy" now. I just figure that the synthetic is cheapo insurance even if the difference is something I can't feel, I remember reading somewhere that the lubrication film strength is higher on the synthetic oils than the dino oils and that is good enough reason for me.

[KJ] I have MT90, but plan to use MTL next time, since I don't drive on the track and the cold start shifting should improve a bit.

[TL] I called Red Line customer service regarding the oil. They actually recommended MT90. They said the viscosity of MT90 is similar to 10W40 or 10w30 engine oil that Acura use. They also said that Comptech also use MT90 for their RealTime NSX. the MT90 is good when the engine warms up but in cold weather, ~40F, it is really hard to shift into first or reverse to get out of the garage.

[TS] Well, for years I saw first hand the advantages of MTL as it did wonders on Hewland MK9 (4 and 5 speeds) as well as on FT200 straight gear trannies. What it did on my NSX was very clear and without any doubt. It simply made 1-2 shifts grind. I don't know why!  I witnessed the MTL fillup and the level was OK.

[WME] If you drive high speeds it's better to put a good synthetic oil in the tranny instead of the OEM mineral oil that tends to foam. That can cause a leakage (it did at my car) which is not only dirty but also dangerous (oil at the brakes).
Since I have the synthetic oil in the tranny everything is okay.  This is the official recommendation of Honda Germany for autobahn use.

[See also Troubleshooting - Transmission for info on this issue]

[JM] The senior NSX tech at one of the recent SE events and I got into a discussion of this with regards to the synchro crunch I was having when the engine was cold. This fella is a lifetime mechanic, who has worked on Mercedes', Ferrari's, and now Honda/Acura. His knowledge of the NSX and automobiles in general is impressive.

Seems Honda designs a damn good manual box, but didn't put too much thought into their early decision as a company to go with motor oil as tranny oil.

Then they noticed a lot of well-designed trannys on multiple models were failing. Seems the motor oil wasn't up to snuff. Just as with Honda Coolant, which is widely accepted as one of the best thought-out and functioning coolant in the business, they sat down, drew out the specs they wanted from a tranny oil and came up with it recently.

Check with your Acura dealer-- Honda manual transmission oil. Got rid of my gearbox problem.

[KS  - 99/3/99] I've been using Redline MTL for the past two years and have noticed no difference from prior to that when I used Honda fluid.

[HS - 99/2/25] Either MT90 or MTL are OK according to Comptech. There's little difference between the two. If you're a racer, use MT90.... for street/track use MTL. Upon switching to MTL I noted just a slight improvement in shifting. I  have have only noticed minor IMPROVEMENTS to the performance of my '91 after starting to use Redline MTL in early 1997.

[AV - 99/2/25] A while back, I replaced my transmission oil with Redline MTL, upon recommendation by several listmembers at that time claiming better shifting and overall performance. I almost immediately noticed an increased "roughness" in shifting, and an increased tendency to "crunch" the gears. I was very uncomfortable with this, so after about a month, I headed back to the dealer and had them replace the transmission oil back to factory oil. Almost immediately, the transmission felt like it used to... it felt smoother, better, and without the "crunching."


When Should I Change ALB Fluid?

[KJ] The Anti-Lock Brake (ALB) system fluid is separate; it does not mix with the brake fluid. Thus changing the ALB fluid is purely a precaution against corrosion due to absorption of moisture over time. It shouldn't need to be change more than once every few years.

What Coolant Should I Use?

[A/H, KS] Recently, several people have questioned whether the coolant (anti-freeze) sold by Honda and Acura dealers is different from the popular mass-market brands.

Honda has sent the information attached below to its dealers. While you might not expect the source to be exactly unbiased, it does provide technical information and justification for differences in their formula.

Genuine Honda Coolant is the Only Way to Go

Increasingly severe operating conditions and the advent of lower maintenance requirements have resulted in significant changes in the variety and the concentration of additives used in engine coolant. Also, the continual improvements in engine and vehicle design have challenged coolant suppliers to design products that perform well in a more demanding environment.

To meet these needs, Honda engineers have developed a superior, high-quality coolant that has several advantages over the competition.

Some antifreeze, although labeled as safe for aluminum parts, may not be compatible with Acura cooling system components. Extensive research and testing by both Honda R&D and CCI, the manufacturer of the Honda coolant, have proven that the abrasive silicates and/or borates found in most domestic coolants can cause these problems:

- - Silicates bond to the surface of the water pump seal and act as an abrasive, causing considerable seal erosion and coolant leakage. In actual tests, the silicated coolant caused early leakage. This leakage increased dramatically until a substantial portion of the coolant had been lost. In contrast, the Honda coolant had almost no leakage through the duration of the test.

Chart here, entitled "Coolant Leakage from Water Pump Seal", showing Leaked Coolant Volume in ml as follows for each test duration in Hours:

24 hrs: Honda Coolant 0, Typical Silicated Coolant 21
48 hrs: Honda Coolant 1, Typical Silicated Coolant 36
72 hrs: Honda Coolant 2, Typical Silicated Coolant 47
96 hrs: Honda Coolant 2, Typical Silicated Coolant 55
120 hrs: Honda Coolant 2.5, Typical Silicated Coolant 56
144 hrs: Honda Coolant 3.5, Typical Silicated Coolant 57
168 hrs: Honda Coolant 4, Typical Silicated Coolant 58.8
192 hrs: Honda Coolant 6, Typical Silicated Coolant 63
200 hrs: Honda Coolant 6, Typical Silicated Coolant 64

- - Silicates tend to gel and settle in the coolest parts of the cooling system, causing radiator plugging and overheating.

- - Borates cause pitting corrosion on the cylinder head.

- - Silicate inhibitors are difficult to stabilize and, therefore, limit coolant shelf life.

Most commercially available coolants were originally designed for cast iron engines. Silicate, an inexpensive additive, was added to coolants to prevent aluminum corrosion, but the long-term durability of the combination was not tested.

In contrast, Honda coolant was designed specifically for aluminum engines. It contains an organic corrosion inhibitor instead of silicate. This superior formula gives these advantages:

- - No silicate abrasion of water pump seals. For example, these graphs show the surface roughness of two aluminum water pump seal rings. Seal A, exposed to silicated coolant, shows considerable damage. Seal B, exposed to Honda coolant, displays only minute wear.

[graphs here, showing roughness across the surface, with A a very wiggly line, and B a very smooth line]

- - No plugging or overheating caused by silicate gelling.

- - Excellent corrosion protection for aluminum components.

- - Long-term corrosion protection for other cooling system materials (steel, cast iron, copper, solder, gaskets, seals, and O-rings).

You can find less expensive coolants on the market, but now you can see why genuine Honda coolant is the only coolant approved for Honda and Acura vehicles (it MUST be used for warranty repairs). Honda's non-silicate formula delivers added protection not offered by 95 percent of other brands. Since our customers expect lower maintenance, you're doing them an injustice if you use any other coolant.

[MBA - 99/9/7] The coolant sold at Honda Dealers is the same part number as Acura stores sell, so try your nearest Honda dealer if your Acura dealer is far away.


Redline Water Wetter

[MBA - 99/9/7] I must qualify my next statement by saying that I sell Redline water wetter. I also use it in all my cars because the stuffs awesome. I live in the worlds best coolant testing area, Phoenix Az, and I find that the stuff lowers coolant temps 20-25 degrees (f), as measured with my surface scanning digital pyrometer. If you live in a hot climate, its the best 7.95 you can spend.


Windshield Washer Fluid

[GM] I recently tried Rain X Plus Windshield Washer Additive. I've used a similar product from PS21 for years and it has worked very well. These products help the water in your washers remove bugs and grime. The Rain X stuff is terrible!!! It does a very poor job of removing grime. Instead it smears it around badly. Worse it leaves some kind of tough residue on the paint and glass. This residue is hard to remove, needing glass polish on the windows and HD Cleanse on the paint. The residue builds up as white gooey stuff in the corners of the windshield and is very hard to remove. Yuck! Stay away from this stuff. It's a pink liquid sold in a tall plastic bottle with a pre-measured cap device attached.


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