I posted this in another forrum. And i should of probably posted it here.


im thinking about going down to the drag strip this friday, and
i'll be making at least 5 runs probably. Now I am currently running 10W-30
Mobile1 Synthetic. Im thinking about putting some Valvoline 50W racing
oil, my car has 206000 miles on it (maybe a rebuild at around 100,000 not
sure). Now is it true that running the 50 weight will protect my engine
better (bearings etc.) by being thicker? Just for the same reason you use
70-90 in the rear? Well i hope someone here nows wut im talkign about and
can help!!!


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88' GTA 350 MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass

 

50 weight isn't good for much of anything. Its very hard to get flowing. I do tend to appreciate multiviscosity oils that act like 50 weight at high temperature. Straight 50 weight is liable to cause more damage than good. I believe it got started as a racing oil by people who ran very large bearing clearances. Since the clearances were high it took a very thick oil to get the pressure back up. Straight 30 weight is ok but I can't think of a reason to use it instead of a multiviscosity oil. 10W-30 isn't a bad choice, racing or not. I lean towards heavier stuff in the summer time. W30 tends to thin out too much on a hot day. 10W40 or 20W50 seems to be better for summer driving. If anything it might be better to run a thinner oil when racing. Generally you run with the engine warm, not hot. The engine needs its lubrication. So its easier to get the oil flowing right without being at full temperature with a multiviscosity oil. Just don't go overboard like a 0W or 5W. Those seem to actually cause more wear because they are so thin, especially cold. Somewhere I remember seeing a tech bulletin to stop putting 5W30 oil in cars, even ones that called for it. They were finding the engine short lived if it was driven for more than a short trip.

 

For occasional strip use, the 10w30 synthetic is just fine. An all out race engine needs something a little better. I use Castrol 20w50 from Walmart in my race engine however I haven't been able to keep an engine together for very long this year to get any life out of the oil. Something about antifreeze and oil just don't mix very well.

There are oils out there specifically designed for race engines. Many racers who run alcohol (methanol) swear by Torco oil.

Your engine has a lot of miles on it. 10w30 may be a low limit for oil choice. 10w40 or 15w40 may help keep the oil consumtion down and a straight 50 weight is just too much.

Also may drag racers run synthetic oil in the rear diff. Usually 75w140 or 80w140 but I don't know how well it will work with a posi since most use some sort of spool.



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Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block

Best ET on a time slip: 11.242 altitude corrected to 10.89
Best MPH on a time slip: 121.52 altitude corrected to 125.89
Altitude corrected rear wheel HP: 497.9
Best 60 foot: 1.546

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

Your car isn't going to need racing oil. If you run sustained RPMs above 7 grand, then perhaps because racing oil typically has more anti-foaming additives. The Mobil 1 10W30 will provide more protection for you than a petroleum 50 weight, even if it's called "racing oil", for your 1320' trips. "Thicker" does not automatically translate to "better protection": Film and shear strength are what provide bearing protection, and that's more of a function of the lube base than it is thickness.

You are also victim to the common misconception about the weight rating differences between engine oil and gear lube. A 30 weight engine oil and a 70 weight gear lube are just about the same viscosity. They have different numbers so people won't put engine oil in their hypoid gearbox and vice versa.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam and intake, World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

[This message has been edited by five7kid (edited July 09, 2001).]