z3bra

Well damn the only stuff I can find on the Castrol website now is the 5w-40 R4 superbike stuff but I could swear I saw some 20w-50 of the R4 at the dealership. I was thinking of looking into the Shell Rotella-t 5w-40 synthetic too, aka diesel truck oil. I don't think I've heard anything bad about that stuff anywhere and you can't beat the price at $13 or so for a gallon at places like Wal-Mart. It's pretty heavy duty stuff without all the marketing hype like Mobil-1 and most other traditional car oil synthetic versions have (Syntec, Valvoline synthetic, Pennzoil synthetic etc).

z3bra

I have to disagree with your mechanic there, given that water is very polar and oil is very non-polar, there's no attraction between them on a molecular level. This is commonly evidenced by them not being miscible with each other. I could go on and on about this but again, put simply, polar and non-polar liquids just don't like one another and will not be attracted.

An oil filter is there to catch pieces of your engine's metal and other parts that wear off in places where the oil film is not sufficient. These particles of debris are then flushed away by the oil and flow through the engine. If they don't get caught somewhere else first, the filter is where you want them to get caught. Even the best oil filters only catch particles down to 8 microns and a water molecule is a hell of a lot smaller than that. Since the oil in our cars typically operates above the boiling point of water, any water that does make its way into the oil will literally boil and once it makes it back to the crank case will be sucked out as a vapor from the top of the OAS when everything is working like it's supposed to. The chemical reaction of combustion when it's not ideal can create acids at times. Acids are also quite polar but some can be more likely to be attracted to the oil than water is and cause buildups and corrosion. Just the same the molecules of acids are much smaller than a filter can pick up and the only way to get rid of the buildup over time is by changing your oil.

I would agree that if you're changing your oil every 3000 miles, you're not likely to get too much buildup of acids whether it's synthetic or dino oil. The bigger issue, particularly on a 951, is the thermal breakdown of the oil molecules. This is where synthetic oils have a definite advantage in that they are an engineered molecule and can be designed to tolerate the high temperatures better than a refined petroleum based oil molecule found in dino oil. The reason they leak so easily is that being an engineered molecule, they also have better cold flow characteristics designed in and consequently lower surface tension at low temperatures which is definitely good for getting oil pumped into the engine from the pan during a cold start, but bad with regard to making its way past seals, particularly seals with some wear on them already.

I'm not sure I agree with his claim on the 928 engine either. I doubt the original 928 engine was designed around Mobil-1 or in that case our cars would be as well given the common design features. Possibly that's true with newer 928 engines with newer manufacturing standards and tighter tolerances, but even that's highly debatable, you could certainly do worse than Mobil-1 for oil, but I suspect any good synthetic of the same viscosity would be perfectly acceptible if not even a little better given the way Mobil-1 has been going downhill lately.

wasteg8

I've had great experiences with AGIP's 10-60 racing synthetic. My car is almost exclusively a track rat--and I found the AGIP runs cooler than Mobil 1 by at least 10 degrees. After breaking in the new motor(thanks John!) for about 900 miles on Castrol 20-50 dino--I'm filling it up with AGIP this week for 3 days at VIR.

Evan70

I have to say I'd really recommend finding a new mechanic. An oil filter will not trap water, and the turbo heat will actually reduce water buildup in the oil, NOT increase it. Water buildup in oil is from not getting the oil hot enough to boil off the water, usually caused by lots of short trips in non-turbocharged engines.

As to his thoughts on the 928, that's really ludicrous. The Corvette has also come factory fill with Mobil1 for well over a decade and there have never been any issues with switching to other synthetic oils. As a matter of fact, many serious Corvette enthusiasts (those doing racing/track days) find better performance switching to other oils (those I mentioned before). And when I say better performance, I'm talking about validated results from getting the oil analyzed. Also, the tolerances on the engine don't really have much to do with needing synthetic or conventional oil, that has more to do with the viscosity. Conventional versus synthetic has more to do with oil life and heat tolerance before breakdown. The LT1 and LS1 engines in the Vettes have very tight tolerances as well, but are also used in several other cars besides the Vette and came with standard conventional oil. Why did GM use synthetic for the Vette and conventional for the other cars? 1) because they worried the owners of the other models wouldn't want to pay the premium for conventional oil, and so used the standard dyno oil/3000 mile change and 2) because they believed most of the drivers of the other models wouldn't be doing the performance driving to need the benefits of synthetic oil.

If you really want some more info on all this, as well as the oil bible I linked earlier, you can also check out the "Bob is the oil guy forum":
http://theoildrop.server101.com/cgi/ultimatebb.cgi?
They have loads of folks doing actual testing on their oil and posting the results, and Mobil1 is by far the worst of just about any synthetic.

hosrom_951

I switched from Mobil 1 0w-40 to Total 10w-50, the reason for the switch was because of oil viscosity in my weather condition (the 10w-50 is much bettwe suited).

The difference between the Total and Mobil 1 was that with Total, oil consumption is greatly reduced (when on boost) and the engine is quieter.

But i was expecting this since the Total oil is thicker, we run Mobil 1 on all our cars, no problem. But the 951 has it's own ways sometimes

95Juan

I run Mobil 1 full synth 15W-50, no leaks......ever, good idle, good everything, and my oil is always clean. i guess i really did finally get a car with a good motor (past cars that died from having bad motors- '83 Poopra, '91 Eclipse GSX). anyway, i guess i'll be switching over to valvoline or royal purple.

............the motor does consume oil like crazy when i'm on boost though.......any suggestions?

M758

I have run 3 oils for a few years.

My 125k mile 951 street car has gotten Valvoline 20/50 racing DINO oil for many years. Runs good on the track and on the street, I did run a 60w version of the same stuff, but that was when I was tracking the the car on hot days. The 20/50 is better daily oil. Do remember I deal with temps from 40 F to 115F. I am afarid of sythenics in the car as they will find all the leak areas the dino oil does not. Once I rebuild the motor I probabl will go to a syntheic.

My 944 NA race car used Mobil 1 f15/50 or along time. Ran fine, but I did notice the oil pressure dropping after 20+ min on the track. This happend on warm and cool days. I switched to AMSOIL 20-50 Series 2000 Racing oil. It is expensive at $8 or so a quart, but it maintains oil pressure for extended runs on the track. I believe this to be some of the best oil I can run. It does not leak in my race motor since it has been rebuilt. I do however feel that it is overkill for street driven car. The only way it becomes cost effective is since it Twice the price of a normal sythenic you need to run it twice as long. 6k miles at least in street car. Of course their promtion say the oil is good for extended drain intervals.

Not sure exactly which Oil I will use in my 951 once I rebuild the motor.

M758

My 951 burned oil before I replace the valve stem seals. Once I replace them my oil consumption is minimal. Even with a oil leak that puts oil on my cross over pipe that can create a nasty smooking effect my oil level says very constant.

I'd bet oil buring from most 951 is a result of old valve stem seals.

streckfu's

I don't know if you're considering it, but do not use motorcycle oil in your car!

95Juan

i did my last oil change about.....1k or 1.5k ago, i've added 3 quarts, but that was only after the Bay Area Drive this weekend (mountain driving with 130 of europe's finest machines), should i be changing soon to something that consumes less?

M758

The problem is not the oil. The problem is that you are burning it. Changing the oil won't solve that problem as it not the oil's fault.

badcoupe

all of my exhaust valve guides were shot when I removed my head I had some consumption issues too. Whebn the guides are bad the seals certainly can't perform their job. If the car sat for a few days when I would start it it would smoke for a few. The engine guy that builds my drag car motors says royal purple is best synthetic on the dyno but he quit using it because a motor that had used it was sitting for 3 months and when they tore it down the crank had surface rust. It had been sitting in the guys trailer. He syas best conventional for HP is kendall but says that doesn't mean it's necc. the best oil he likes the valvoline race oils well for street/track cars. I have a drum of pennziol synthetic I got from Panther racing the IRL team, the guy that built our full midget motors also built all of panthers IRL back then when they ran Olds motors. It's 5/50 weight I use it in both cars. And yes oil temp does get rid of the water that comes from condensation, thats why you don't hammer on your car till the oil temp is up to boil the water off. This usually happens at around the 120 mark IIRC

hosrom_951

If it is burning oil when on boost and not when off boost, the turocharger is showing it's age.

You are allowed 1.5 liters of oil for every 1,000kms according to the manual.

95Juan

should i switch over to something like a lindsey sport? i'm in need of quick spool up, since most of my driving in the future will be mountain driving against an FC3S, and my 951 is a daily driver, not a dyno/track queen. i have to admit, i do have my foot in it a whole lot . before the last oil change, it had gone 3000 miles and was 2 quarts low. i ran the **** out of it for 2 or 3 days in a row (crazy weekend) and i was 3 quarts low. should i be changing out my turbo soon? i'm guessing it hasnt seen a rebuild in a while.......or ever.

TRWright

If you want something that makes crazy power with a broad powerband, check out the Vitesse Stage 2. That is what I have. It makes more power than anyone needs (over 400 RWHP is fairly easy to achieve on higher boost), and spoolup is pretty amazing. I have no experience with the Lindsey sport turbo, or any of their turbos for that matter, but you can start a thread and ask about it. People who have actually used them will chime in.