oil question

steve remchak · **Posted:** Sat Apr 16, 2005 12:41 am

anybody else running mobil 1 synth 15/50 for autocross? i have one school, one autocross, and maybe 200 miles of spirited around town driving and the oil is still almost the same color as it came out of the bottle. the bmw does seem to burn it out some however. no leaks that i can find and i filled to spec so i guess it is burning off.

DickRasmussen · **Posted:** Sat Apr 16, 2005 9:10 am

I use it in my formula car's engine.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

I run the Mobil I synthetic 5w30 and the Mobil I filter all year long now. I tried the 15w50 last summer and didn't notice any improvement when it comes to autocross or oil temps. I usually left the oil temp displayed and it never got that hot. Autocross is just too short a run. Even on 60sec courses at Laurinburg in June/July. Then again I seldom bang the rev limiter since I just jump into 2nd off the start. And we haven't had a course yet that I hit red line in 2nd.

DickRasmussen · **Posted:** Sat Apr 16, 2005 9:32 pm

Steve,

Regarding the 15W/50 Mobil 1 for autocross: Do you have a question or concern regarding using it?

You probably don't "need" it for your BMW since it is a modern engine and autocrossing doesn't abuse the engine. (Conversely my formula car engine is a very old design and it typically is ABUSED with lots of heat and rev limiter time).

You probably shouldn't run oil heavier than BMW recommends. However any good synthetic oil probably won't be a problem even if it is heavier than recommended since synth oil flows so well cold compared to dino oil.

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

steve remchak wrote:

anybody else running mobil 1 synth 15/50 for autocross? i have one school, one autocross, and maybe 200 miles of spirited around town driving and the oil is still almost the same color as it came out of the bottle. the bmw does seem to burn it out some however. no leaks that i can find and i filled to spec so i guess it is burning off.

I use red top (now yellow?) 15-50 M1 in both my E36 and E30. Been doing that ever since I got both cars based on "internet wisdom". Hardly burn any oil on the street, E30 burns a little oil on track.

Rich Anderson · **Posted:** Sun Apr 17, 2005 8:30 am

I do not know what the recommended weight is for your car (or what kind of car you have for that matter) but for street and autocross use, there is rarely a need to go to a heavier weight oil. Heavier oils generally maintain a higher HTHS rating (High Temperature High Shear) which can be useful for on track driving, but autocross is generally so such short duration that the oil does not have time to reach a high temperature. For reference, the HTHS test pumps 302° oil through a diesel injector. If you have 302° oil temps at autocross, I suggest that you have other problems that an oil viscosity change alone cannot solve.

There are exceptions, just like everything else. Some cars shear oil because of their design. This is true of a lot of DOHC engines with cam-on-bucket solid lifters. Other cars have a weakness in the oil system where extra film strength may make-up for a poor factory oiling design.

So why not go to a heavier oil? First is power. Thicker oil takes more force to pump. Now, most of here will trade protection for a couple of hp, so this is most likely not an issue. Second reason is protection. A heavier oil does indeed have a stonger film strength. However, this is good and bad. The film may not adequately lubricate in some of the tighter engine clearances, such as those on the aforementioned tappets. If the oil is too thick, it cannot make the film necessary for protection. My worry is that since you are autocrossing, you may have colder oil at the start of your runs (180°) and it is at this time that the oil will not be able to provide protection. If your engine recommends a 5w-30, at 180°, your oil will be A LOT thicker than the designers intended. Look at Redline's site and you will see that they expressly caution against using their 20w-50 at temps under 225°. The final problem is one that is unlikely to appear - pump cavitation. Very thick oils can, in fact cavitate in the pump. As everyone knows, air is a poor lubricant.

My general rule of thumb is that you can safely move up one weight without any worries. If your engine recommends 10w-30, a 10w-40 will be just fine. I would, in that case recommend a 5w-40 HDEO sytnthetic such as Rotella T Synthetic or Mobil Delvac 1 because that will ensure that the viscosity curve in the middle of the range (the warmup cycle) is almost identical to what the engine was designed for.

This is all general guidlines. As said before, there are many specific engines that have parts that break them. Early hydraulic lifter Ford Zetecs recommended 5w-30 or 10w-30, but going to a 10w-40 caused the lifters to stick and the valves to stay open. Clearly the rule of thumb that you can step up one weight without consequence does not apply here.

steve remchak · **Posted:** Sun Apr 17, 2005 10:29 am

thanks for the input. i can't seem to nail down what bmw reccomends for oil. it may be 5/30 but they list a range between 5/30 to 15/40. my concern was more "am i doing more harm than good with the 15/50" i may back down to a 10/40.

Keith Quistorff · **Posted:** Mon Apr 18, 2005 9:11 am

Steve,

Sorry, I don't recall which model BMW you have, but if it's an E36, I'd recommend staying w/M1 15W-50. I've tried going to lighter weight oils in each of my E36's, but I've always gone back to 15W-50 if the car is going on track or being autocrossed.

The problem w/the e36 in-line 6 engines (with the exception of the '95 M3 LTW w/its dual pick-up oil pan) is they have their oil pick-up on the right side of the oil pan, resulting in oil starve on high-G right hand turns. The problem is obvious, especially on R compound tires, at the end of an autocross run - your (hydraulic) lifters will tick for several minutes as a direct result of temporary oil starvation.

High viscosity oil sloshes around the oil pan less than lower viscosity, which helps with the oil starvation issue. The other thing you can/should do with an E36 is run the oil level 1/2 to 1 quart above the full mark. BTW, this isn't just me saying to do this, it's the overwhelming majority of the E36 community. I even discussed it with James Clay at BimmerWorld, and rather than try to sell me a modified oil pan, he also recommends just adding an extra 1/2 to 1 quart.

If you autocross an E36 BMW and also drive it off season during the winter, consider using a lower viscosity oil during the off season (at normal fill level), then switching to M1 15W-50 before the first autocross. I generally wait until the day of the first autocross to overfill the oil, I add the extra 1/2 to 1 quart at the first event, then check it just before each event during the season in case the level drops at all (add as needed to keep it at the same overfilled level).

Ryan Holton · **Posted:** Mon Apr 18, 2005 9:16 am

I dont really have any words of wisdom here, but if you wanna read about oil until your eyes bleed:

www.bobistheoilguy.com

GOOOOODDD tech on oil to be had there. That is a site full of oil nerds.

They (and Rich Anderson) are the reason I am using the Rotella Tsyn 5w-40, works as good as Redline and costs 11.78/gal at Wal Mart.

Kevin Butler · **Posted:** Mon Apr 18, 2005 12:43 pm

I've got a higher mileage Miata (115k) that appears to have had dino oil all of it's life. The oil also gave the indication that it had been rode hard and put up wet. I've been flushing out the block for the past few months with 1500 mile oil and filter changes.

I'd like to upgrade to a synthetic oil soon. However,last year I asked a performance import mechanic what he thought about upgrading from dino to synthetic, and he said,"what would you want to do that for?" He continued if I was really insistant on making the upgrade, to go up a weight (Mazda specs 5W-30). The heavier recommendation was to account for wear already experienced by the engine.

Anyone have a good experience/recommendation for such a synthetic upgrade?

Vincent Keene · **Posted:** Mon Apr 18, 2005 12:47 pm

Kevin Butler wrote:

Anyone have a good experience/recommendation for such a synthetic upgrade?

Ryan Holton wrote:

I am using the Rotella Tsyn 5w-40, and costs 11.78/gal at Wal Mart.

I'm using the Rotella T Synthetic 5W-40 also in my Z-24 and the Miata.

Rich Anderson · **Posted:** Mon Apr 18, 2005 12:58 pm

I feel that the Rotella T Syn, Delvac 1 or other 5w-40 HDEO is an excellent match for the Miata as the increased detergent levels should help with HLA noise. Plus, in your specific case, the HDEO's increased quantity of detergents and dispersants necessary for diesel soot control will be helpful in dealing with any remnants left from previous hard use or poor oil quality. Plus, you will be going up one grade so that will keep the mechanic happy even if it is a synthetic.

steve remchak · **Posted:** Mon Apr 18, 2005 6:23 pm

rotella 15/40 synth in the truck. mobil 1 in everything else. thanks for all the info. i beleive my question has been answered. now as long as my parts come in (i am such a dumbass, torque wrenches should not be sold to just anybody) from bmw i will be good to go. thanks again everyone.

Rich Anderson · **Posted:** Mon Apr 18, 2005 6:41 pm

steve remchak wrote:

rotella 15/40 synth in the truck.

The 15w-40 Rotella is not synthetic. The synthetic Rotella is 5w-40,

steve remchak · **Posted:** Mon Apr 18, 2005 7:30 pm

yeah, sorry. i misspoke. i am running 5/40. ford 6.0 diesel has a condition called "the romps" and the rotella has pretty much cured mine. been using it for 10-12k miles and a noticeable improvement over dino juice. unfortunately, i can't extend change interval much past 6k.

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