Engine Oil Analysis / Oil Change Interval

[Lucid Moments]

Anybody ever do engine oil analysis to really figure out how long you can run your oil?

 

I've blown up a couple of motors due to reasons that I think I've got figured out. Of course I thought I had it figured out before I blew the last one and it turned out I was wrong. So in a case of probably ridiculous overkill I have been changing the oil prior to every track weekend. Using Amsoil 10-40 at not quite $10 a quart that gets a little on the expensive side.

 

So I'm sending my first sample in to Blackstone labs to see what I can see.

 

I realize that every engine is different, but just for giggles has anyone ever done this to determine oil change intervals on a track day car?

 

For that matter even if you have never done this how often do you change the oil in a track day car?

[DanSTi]

I've used Blackstone before, their analysis can be pretty useful in determining how healthy your engine is but not necessarily for determining change intervals. I found that even after one track weekend, there were a fair number of contaminants in the oil, mostly copper bearing material, and it had sheared down significantly. I always change my oil before every event, it's worth the $50 or less for the peace of mind.

[brant giere]

There are many variables...and each car and engine are different so it is very hard to generalize. With that in mind i use Redline 10w40 in both my 944 NA and 964 cup engines. UOA's are still fine after 10-12 hours of racing. A Subaru engine may have sheared this oil in 5 hours so please take it for what it is worth. My recommendation is to do a series of UOA's over a 2 year time frame and look at trends. Do not do just one and make assumptions....Use a very high quality oil. I cannot stress this enough. Junk oil will turn your engine into the same!

[thonczarenko]

I have an American Iron Mustang ('89) 302 with 90k miles. The oil came back with low contaminants, wear metals, additive metals in all categories. Copper and Aluminum were both at 3ppm, water was less than .1. Fuel was less than 1% and Soot was less than .1%. Just to name a few.

 

I used Mobile1 15w-50, and had about 1500 miles on the oil when analyzed. Oil was new at the start of the season with a few hundred miles from driving on the street for testing, and the rest is practice, qualifying and racing.

 

I tried to upload the image of the analysis, but I was unsuccessful. Anyway, I hope this helps!

[hustler]

Here's that "High Zinc AMSOil 10w40" you're probably ordering at $50/g compared to $19/g Rotella Synthetic from Wal-Mart on my turbo Miata:

Most notably, the Rotella has more zinc/ZDDP than the AMSoil which markets it's high-zincnes; there's also significantly more moly in the Rotella. The rest of the data that I care about puts them pretty close together considering calcium, phos, and slightly better viscosity at 200*f. I attribute the major drop in iron to engine break-in (look at mileage numbers) and dropping oil temps from 290*f to 220*f with new oil cooler ducting.

 

I use the UOA data to determine that roughly 4-tracks days or two weekends put enough fuel in the oil that I need to change (11.5:1 AFR). I'm considering running the cheaper, $11/g dino Rotella because I'm not wearing out the synthetic oil, I'm shearing it with fuel. We're running 8 race weekends on my buddy's naturally aspirated Miata with this oil.

 

I still send a UOA in twice per year to tell me what the bearings are doing. When I get a spike in metals I'll know it's time to look at the bottom end.

[Lucid Moments]

Forgot to update this thread. Got the UOA back, here it is.

 

The main thing I have to figure out is why I have so much fuel in the oil. I'm going to check and see if my injectors are leaking. I also didn't follow the sampling procedures properly. It was a cold sample and the engine had idled a few times before pulling it, loading and unloading from the trailer and such.

 

As to the breakdown of the oil. I am using this oil on the advice of a friend of mine who is a mechanical engineer. His particular concern was for the High Temp High Shear factor of the Amsoil. I don't know what that value is.

 

My current plan based on this UOA is to change the oil prior to my next track day which will be Road Atlanta next month and take a hot sample and see where that takes me.

[hustler]

The main thing I have to figure out is why I have so much fuel in the oil.

What is your target, sustained AFR on the track? If your tuner is not a moron, which is unlikely though possible, its richer than 12:1, and that's where the fuel comes from.

I'm going to check and see if my injectors are leaking.

Do you think they are leaking into the engine?

As to the breakdown of the oil. I am using this oil on the advice of a friend of mine who is a mechanical engineer. His particular concern was for the High Temp High Shear factor of the Amsoil. I don't know what that value is.

That would be viscosity at 210*f, which is no different from my Wal-Mart oil. AMSoil makes great oils and gear oils, but that oil simply does not out perform Rotella Synthetic.

I also didn't follow the sampling procedures properly. It was a cold sample and the engine had idled a few times before pulling it, loading and unloading from the trailer and such.

The idea is to stir-up the crap in the bottom of the oil pan, you don't have to do it right when you pull off the track. I'm pretty sure 250*f oil will melt that plastic container.

[Lucid Moments]

The main thing I have to figure out is why I have so much fuel in the oil.

What is your target, sustained AFR on the track? If your tuner is not a moron, which is unlikely though possible, its richer than 12:1, and that's where the fuel comes from.

It was tuned by Ed Senf at Balanced Performance in Atlanta. IIRC he set the a/f at 11.5:1

I'm going to check and see if my injectors are leaking.

Do you think they are leaking into the engine?

Its a possibility that I would like to rule out.

As to the breakdown of the oil. I am using this oil on the advice of a friend of mine who is a mechanical engineer. His particular concern was for the High Temp High Shear factor of the Amsoil. I don't know what that value is.

That would be viscosity at 210*f, which is no different from my Wal-Mart oil. AMSoil makes great oils and gear oils, but that oil simply does not out perform Rotella Synthetic.

I'll have to take your word on that. I'm going to stick with the Amsoil for now until I get a good set of data. My main concern is the condition of the engine after all.

I also didn't follow the sampling procedures properly. It was a cold sample and the engine had idled a few times before pulling it, loading and unloading from the trailer and such.

The idea is to stir-up the crap in the bottom of the oil pan, you don't have to do it right when you pull off the track. I'm pretty sure 250*f oil will melt that plastic container.

By the time I run a cool down lap and get back into the paddock my oil is usually down to about 200. But I get your point. I'll give it a little while before I pull the sample. It will be end of the day on Sunday so I won't be in a real hurry anyway.

[DanSTi]

If you sample cold oil after a couple of startups, you're going to see more fuel in the oil than normal. When you send in your next sample, bring the oil up to temp, let it cool enough to be handled, then take your sample. Let a little bit drain out before you fill the cup, you don't want the very first or last stuff that comes out of the pan.

[Lucid Moments]

If you sample cold oil after a couple of startups, you're going to see more fuel in the oil than normal. When you send in your next sample, bring the oil up to temp, let it cool enough to be handled, then take your sample. Let a little bit drain out before you fill the cup, you don't want the very first or last stuff that comes out of the pan.

 

I use a siphon to sample the oil, that way I can do it without having to change the oil.