Any reason NOT to run Motorcraft 5W-20 if you track your car?

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09-22-2011, 09:55 PM

#11

Import_Slaya

2nd Gear Member

Join Date: Apr 2008

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Posts: 187

Quote:

Originally Posted by DPE

Interesting read. The Scott guy certainly has the qualifications it looks like. Yet experience in this thread and actually in that thread further down indicates 5W-20 to be fine, does it not? I'm not trying to make an argument, especially 'against' Scott, who clearly is the resident athority on the subject, but the thing I haven't yet seen is a failure attributed to 5W-20 (not to say it hasn't happened, or perhaps my reading compreshension is bad, but I haven't seen it). The thing I have seen is a number of people running 5W-20 that don't have any issues, including guys that have run it for quite awhile in older Mustangs.

Sign up and PM him. I did, and I think SoundGuyDave did (or he spoke with him in person at an event a few years back). He's very helpful, but can be tough to get a hold of (he is now an engineer for a NASCAR team). The only reason why Ford specs the 5w20 is for CAFE mileage averages. Our same car overseas specs a 30 weight oil in the owner's manual.

Call me crazy, but when I get an analysis back that shows the oil either isn't meeting the minimum for the weight (or it shears down fairly rapidly under track conditions) and one of the engineers who designed our engine explicitly recommends a heavier weight, I'm not sticking with the 5w20. I've been running 10w40 (Mobil 1) for a few years now without issue. And Mobil 1 isn't necessarily the best oil, but it is a solid choice that is reasonably priced for a synthetic.

Will you be fine if you stick with 5w20? Probably? For me, especially now that I'm out West running in 100+ heat on some track days, I'm going to go with the oil that the engineer recommends, not the oil that the bean counters/regulatory compliance team recommends.

Quote:

Originally Posted by Ansibe

The 5.0 engine is designed to operate with 5w-20 oil at normal temperatures to the engine rpm limit. My track use is within those limits, so I use 5w-20. I warm my engine up carefully so the oil viscosity is stable, and I use a full synthetic to deal with the high oil temperatures seen at the track.

My engine is 100% stock.

And word on the street was that the 4.6 engine was designed to operate on 5w20, with plenty of people saying "your engine will blow up if you run a heavier weight, because the clearances are specifically engineered for a 20 weight oil!" Turns out that was bogus. Register on cc.com and PM some of the guys who race the new 5.0 (or crew for those who do) and you'll get a better recommendation. It may be 5w20, but it may be something different.

Bottom line is that 5w20 will be fine. It may not be the best during more extreme use (e.g. tracking the car, especially in hotter weather), but it should be fine. The information is out there, however, for anyone who is contemplating a heavier weight.

Last edited by Import_Slaya; 09-22-2011 at 09:58 PM.