How often should I change oil in a "race car"?

[robertcope]

I have a 1999 Miata that I use as my track car. It's street legal, with a stock motor and the usual modifications (intake/header/exhaust). I've been running M1 0W-40 and recently moved to Red Line 0W-30. A typical weekend will have me putting, say, 200 to 250 miles on the car. If it were one of my street cars, I'd run 5000 to 10000 mile OCIs depending on UOA feedback, but that feels wrong for a car that sees a lot of track time.

So, how does one find the right OCI for a "race car"?

And in case you're curious, here's some video of a fast lap a few weeks ago:

http://www.youtube.com/watch?v=5KZRuZzsazQ

robert

 

[Oldwolf]

That looks like fun.

Also, it looks like you are redlining most of the time so I don't think normal OCI's apply to you. Others will chime in but I'm thinking a 1000 mile OCI under those racing circumstances would not be too often. I look forward to reading other responses.

You should try the Nurburgring some time.

 

[Cristobal]

You sure as ___ know how to calculate speed on those sharp curves; that's impressive.

 

[Quattro Pete]

How about doing a UOA after about 1 or 2 thousand miles to see how things are going?

 

[robertcope]

Originally Posted By: Quattro Pete
How about doing a UOA after about 1 or 2 thousand miles to see how things are going?


Yeah, may send one off, I guess. I'm just not sure if it should be interpreted any differently? I think I fear it telling me I should go to 5K or more on the oil, though I'm not sure why I use the word "fear".

robert

 

[Lead Shoes]

I would do a 2k UOA and see how the oil is holding up.

There are too many variables to each individuals case in a track car to be able to give a certain number.

 

[CATERHAM]

Since it's a stock engine and you're using a top notch race oil you can easily go 5,000 - 6,000 miles. You're definitely not going to break down the RL lube.
The only limiting factor that I can see would be fuel dilution and if that isn't occuring, and it likely isn't, then there really isn't anything stopping you from a normal OCI.

BTW have you equipped you're Miata with oil temp' and oil pressure gauges? since RL doesn't shear any drop in OP would be an indication of fuel dilution. If the OP stays constant as you rack up the miles that's a good indicator that the oil is fine.
If you're running very sticky R compound tires or even slicks I'd be more concerned with maintaining OP during sustained high G cornering, consiquently an OP gauge is really manditory fitment for any track use if you don't already have one.

 

[robertcope]

Hmm, on one hand I hear what you're saying and it makes sense to me. On the other, I don't know ANY Spec Miata or other race team that would change their oil once every season or two. Of course, it is possible that everyone is wasting a lot of oil. I guess I'll do a UOA and see what it says. I'm just concerned that a $25 UOA may not be catching what matters in this context, or if it does, I'm not sure what to look for.

I don't have an oil pressure or temp gauge in the car. It's definitely on the todo list, but to be honest, it is more for curiosity than anything else. There are so many of these cars running around on the track that I am quite sure that I'm not doing anything that will hurt it.

Good thought on the R-comps, but I've never heard of it being an issue, and I know folks who run a lot more tire than I do. One nice thing about these cars, they're well sorted out as track rats!

 

[Oldwolf]

How many quarts does it hold? Probably not enough to worry about short OCI's I'll bet.

 

[robertcope]

It takes four quarts.

robert

 

[LimitedSlip]

I ran a 1990 in Spec Miata for a few years and changed my oil every third race or so. Most folks changed it every race weekend but I always felt that was way overkill. I have seen a UOA on PP that had four race weekends on it and the oil was doing just fine.

On an 80-90F day my oil temps reached 290F during a 30 minute race. Without drafting I don't think yours are that high.

Probably more important to overkill the oil changes on the diff as those only hold a quart and work pretty hard. You may have a Torsen so YMMV.

 

[Turk]

Originally Posted By: LimitedSlip
I ran a 1990 in Spec Miata for a few years and changed my oil every third race or so. Most folks changed it every race weekend but I always felt that was way overkill. I have seen a UOA on PP that had four race weekends on it and the oil was doing just fine.

On an 80-90F day my oil temps reached 290F during a 30 minute race. Without drafting I don't think yours are that high.

Probably more important to overkill the oil changes on the diff as those only hold a quart and work pretty hard. You may have a Torsen so YMMV.


+1.

Spend the cash for a UOA so you know where you're at with the particulars and go from there. Stay conservative especially if you're going to keep the car a long time.

Nice track run.

 

[Mitch Alsup]

In my opinion, running the oil on a race track is the kind of extreme use where the typical OCI stuff is no longer valid. Running hot (280dF+) oil at redline for dozens of minutes at a time (e.g. no oil cooler) will deplete the additive package--especially the anti-wear parts (ZDDP).

I, personally, don't go to the track unless the oil has less than 1K miles on it, and change it immediately after getting back home. (I drive there, race there, and drive back). For the most part, its the change it immediately afterwards that is important.

In my car which has both oil temp and pressure gauges, I loose 5 PSI after a track day (100-130 miles depending), and even with an oil cooler, I still see 280+/- temps in texas summertime heat.

 

[robertcope]

Thank, Mitch. What do you run? Where do you race? I'm in College Station and Austin, we may have bumped into each other.

robert

 

[A_Harman]

A naturally-aspirated Miata will not stress Redline oil enough to cause it to break down, even if you are running 300F oil temperatures. Fuel dilution would be a more likely cause of the oil thinning out. In the case of a race car, I think the duty cycle would make you consider it as a commercial vehicle, and do UOA's regularly. If you are keeping a log on the car, do a UOA after every weekend on the track, and plot the trend of wear metals, TBN depletion, and fuel dilution over a number of events.

 

[oliver88]

I do 12 hourish oil changes on my Porsche race cars with Redline or Brad Penn and UOA's have always come back just fine at that interval...I am certain i can do 15+ hours without a problem. One is an air cooled 911 with a 12 quart capacity, the other is a 944 with a 7 quart capacity. Oil temps are 240ish in the summer as both cars are equipped with large oil coolers. I see 220ish in the spring and fall races. I cannot imagine a race car would need to have an oil change each race weekend unless you have excess fuel gettiting into the crank or a leaky head gasket letting contaminants in...use UOA's to catch that. Most racers change it "just because" and waste too much money and time doing it. Check your oil for TBN/TAn and contaminants..Wear metals may be watched but do not get too excited if you see lead or copper higher than we normally see in the UOA section here at BITOG...use UOA's to study "trends" and watch for dramatic wear metal spikes as you go forward. My 2 cents.

 

[Gary in Sandy Eggo]

The harder you press the accelerator, the more blow-by products get into your oil. With engines sealed the way they've been for the last 3+ decades, blow-by is your only only source of contaminents. Consequently, hard running would require more frequent oil changes, rather than fewer. Driven hard, you should probably change your oil the proverbial 3K miles, or even more freuently.

Regarding hard driven engines (if that's the majority of your driving), especially in warmer weather (80F+), I'd run conventional monograde SAE-40 oil. If ambient temperatures were running near 100F, and you're driving hard, I'd run monograde SAE-50 racing oil, and if was a big engine, I'd run SAE-50 aircraft oil, and change it after every race. All this assumes you want your engine to be wear-protected under racing conditions.

 

[Robenstein]

I know on my old mans Big Block Checy with Enderlie mechanical methanol injection we had to change the oil pretty much after every race day at the dragstrip. It would get so milky we didnt have a choice.


We used Pennzoil GT racing oil and the engine would last an average of 4 seasons before we freshened it. Not bad for an 900hp engine.