At the risk of severe flaming, I am tossing my 2 cents in.
Two years ago, I tried running Mobil 1 15W50W (I'm pretty sure it was 15/50
- may have been 20/50), in my G production 1600. It seemed to have
significantly worse wear characteristics than my old standby, straight 50W
Pennzoil racing oil. I had much greater wear on the cam followers, and I
think that the oil also contributed to a valve guide dropping through the
head on # 4 inlet, and several other guides pushed into the head but not all
the way through. I also had several #3 rod bearing failures. I have gone
back to the Pennzoil.
Please keep several things in mind here:
1) This is a race engine - it spends >80% of it's time above 6000 rpm and
under full throttle. Loading is much higher than in a street motor.
2) The forces on the valve train are much greater than stock due to much
higher valve spring rates and much reduced cam root diameter.
3) Other factors are in play here - for example the rod bearings may have
not had sufficient clearance or oil flow, and that may have caused the
failures, not the oil. However, I have never had a bearing failure like the
ones I had with Mobil 1, and even the times there was no failure, there
appeared to be more wear on #3 and #2 rods. Also, the valve train was
somewhat aged and tired, that may have been the factor there.
4) I may have been lulled into a false sense of security by the multi-vis
oil and revved the engine higher when it was still cold. I am VERY careful
with the 50W to wait until the oil temp comes up to at least 140 deg before
I take it over the 4000 to 5000 range. I wasn't so careful with the Mobil 1.
5) A final factor in changing back was the statements of several racing
acquaintances (who I respect based on their success and education), against
synthetics in racing applications, and that my engine balancer (who is FAA
certified) told me that synthetics are not allowed in aircraft engines. If
someone who can speak authoritatively knows different, please comment.
One last thing - I did notice a marked increase in engine output that showed
up directly in lap times. I just can't afford to get horsepower that way
except under extreme circumstances (like a particular race at Mid-Ohio in
October).
Once again, this is just my 2 cents, please don't anyone take it personally.
Pete Dehmler
GP 1600
> From: "Hall, Phillip" <Phillip.Hall@msfc.nasa.gov>
> Reply-To: "Hall, Phillip" <Phillip.Hall@msfc.nasa.gov>
> Date: Thu, 15 Feb 2001 08:41:21 -0600
> To: "Roadsters (E-mail 2)" <Datsunroadsters@onelist.com>, "Roadsters (E-mail)"
> <Datsun-roadsters@autox.team.net>
> Subject: Synthetic oil (long)
>
> Hey all -
>
> The question of change intervals and synthetic oil has come up. As a side
> at work we run oil tests using the Shell Four Ball test rig. This tester
> was developed by Shell oil to test the extreme wear properties of motor oils
> - cams, piston skirts etc. It consists of three, = inch balls held in a
> triangular pattern in a cup with oil heated to 165 degrees. A forth ball is
> lowered to the center of the three balls and loaded to 40 KG. The ball is
> then rotated 600 RPM for one hour. After the test the wear scar is measured
> on the three stationary balls. The bigger the scar the lower the extreme
> wear property of the oil is. We use Havoline 30 wt for a base line. We use
> this oil because engineers from the past liked this oil, so we have a large
> data base.
>
> Looking at data shows new Havoline 30 wt has a wear scar of .0165 inches.
> New Mobil 1 has a .0145 inch scar. May not seem like a lot of difference,
> but it is. Havoline 30 at 3000 miles has a wear scar of .020 inches and
> Mobil 1 at 4000 miles has a .0164 scar. Remember - the bigger the badder.
> 3000 miles is as long as anyone was willing to run Havoline 30 wt, so its
> data stops here. Mobil 1 at 6000 miles is .0167, at 8000 miles is .0188,
> and at 10,000 miles is .0194. So, at 10,000 miles Mobil 1 has better
> lubrication properties in the critical areas in your motor then a good 30
> wt. All mineral oils follow Havoline pretty close - major brands. Some off
> brands have a .020 wear scar new. Multi-grades generally have a larger wear
> scar as well. This data was from a 5.0 Ford Mustang. Every motor will be
> slightly different, but not much.
>
> So, synthetic can handle long run intervals. But, that is part of the
> story. You have contaminates to deal with. This is where the additive
> package comes in play. This is the expensive part of oils and the reason
> synthetics are high priced. Because of the long run intervals of synthetic,
> they must have a vastly superior additive package - and they do. Proof of
> this is to take 3000 mile dino oil and look at it in a glass jar - then do
> the same for Mobil 1. The Mobil 1 will look new compared to the dino oil.
> I run Mobil 1 in my new cars to the longest manufactures oil change interval
> - usually 7000 miles. This will keep the warranty happy. In my Roadster I
> change it once a year regardless of mileage. It run my Roadster about 5000
> miles a year. Most people at work run synthetics and do the same. We have
> a bunch of cars in the lot that have over 200,000 miles on them and going
> strong. I (my wife) never keeps one that long.
>
> I run 10w-30 Mobil 1 in my new Roadster motors (after break-in). Older
> motors get 15w-50 because the tolerances are larger. Because synthetics
> don't thin down like mineral oils do at temperature, I would be careful
> running 15w-50 in a motor with a high volume oil pump. By doing so you may
> run into cavitation problems - oil gage jumping wildly. Drag racers
> experience this often at high RPM. Drop a wt and it will clear up.
>
> I checked the auto parts stores last night and could not find a zero wt
> Mobil 1. It was about 2 years ago they were talking introducing this oil,
> so apparently they have in some markets. I stand corrected.
>
> Testing another "magic" oil additive today. It looks and smells like
> linseed oil! This should be fun. Additives are another subject all
> together. Another day, but never tested a good one - none- zip - zero -
> don't waste your money.
>
> Sorry for being soo long. I like synthetics (obviously). If you have been
> to the conferences, seen all the tests and data, and read the lubrication
> journals you would run nothing other then synthetics.
>
> Phil
> SEROC
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