Oil weight for drag racing/street use - Chevelle Tech
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post #1 of 15 (permalink) Old Jun 7th, 05, 2:50 PM Thread Starter
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Question Oil weight for drag racing/street use

Can someone give me an idea of what oil weight to use following break in? Huntville racing (built my shortblock) suggested a 20/50 non-synthetic oil until break-in but didn't really have an opinion after that.

I am currently using Lucas 20/50 race oil. I would like to stay with Lucas but I am wondering if I should run a 10-40 wt. Thanks

Steve

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post #2 of 15 (permalink) Old Jun 7th, 05, 2:55 PM
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Re: Oil weight for drag racing/street use

I use 10W40 in the warmer months,and 10W30 in the colder months in my 70 SS

..theres no reason to use 20W50 in a new motor IMHO
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post #3 of 15 (permalink) Old Jun 7th, 05, 2:58 PM
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Re: Oil weight for drag racing/street use

Unless Huntville Racing built the engine with "race-type" internal clearances, which if they said 20-50 would be my guess. If the motor has 'nominal' clearances of say >00175 to .00250 on the rods and similar on the mains, then lighter would be better. Ask the builder how tight the motor was built.

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post #4 of 15 (permalink) Old Jun 7th, 05, 3:01 PM Thread Starter
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Re: Oil weight for drag racing/street use

It gets to be in the 90's a lot here this time of year and I expect the air temp to be in the upper 80's at the track.. so I'll go with the 10-40

Is there a performance loss in the heavier weight oil??

Steve

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post #5 of 15 (permalink) Old Jun 7th, 05, 3:19 PM
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Re: Oil weight for drag racing/street use

After a good break-in period (maybe a thousand miles or so to get the rings seated good) I would use Mobil One 10w30.

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post #6 of 15 (permalink) Old Jun 7th, 05, 6:05 PM
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Re: Oil weight for drag racing/street use

after breakin 0-30 Mobil 1

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post #7 of 15 (permalink) Old Jun 7th, 05, 7:30 PM
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Re: Oil weight for drag racing/street use

I run 15/40 diesel oil, supposed to have much more sulfer?(I think) I figure if a semi my friend has can have over 25000 hrs on it and not need rebuilt the diesel oil must be good at what it is supposed to do.

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post #8 of 15 (permalink) Old Jun 7th, 05, 7:35 PM
 
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Re: Oil weight for drag racing/street use

I have run Mobil 1 15W-50 for years. Pretty reasonable price at Walmart. Clearances are around .0025"plus. I Know I lose some HP over lighter weights but the piece of mind is worth it. I agree that you need the machinist to tell you what the clearances are. If they are very tight then a lighter weight would be better. A friend with an 800plus HP 498 Hemi gained close to 30HP on the dyno from changing from 20w-50 to 0w-30.


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post #9 of 15 (permalink) Old Jun 7th, 05, 8:59 PM
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Re: Oil weight for drag racing/street use

I run 20W-50 Valvoline Racing Oil and have never had a problem.
Pretty mild temps here

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post #10 of 15 (permalink) Old Jun 8th, 05, 11:01 AM
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Bill R
 
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Re: Oil weight for drag racing/street use

Steve,

I am 'old school' believer in straight weight oil. My recommendation is straight 30W, or if you prefer multi-viscocity then go with 10-30 (my preference is Valvoline) and see how your oil pressure holds up when the engine is warm. 20-50W is too thick for any application, especially a new engine, in my opinion.
To answer your question, yes high viscocity oil will use up some horsepower - but not a whole lot. Think of the difference of stirring molassis as compared to stirring water. Now the volume of open space between the oil pump gears and is not very much, so the drag won't be very great. But the force necessary to transfer the oil through the pick-up screen, tube, etc will be significantly greater with the higher viscocity oil.

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post #11 of 15 (permalink) Old Jun 8th, 05, 12:09 PM
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Re: Oil weight for drag racing/street use

Our old 427 got beat on for upwards of 200K miles. It saw 6500 so many times that I wouldn't even hazard a guess. All we ever used was 10W30 oil. Whatever name brand that was being sold at the local stores would do. The oil got changed regularly along with a Delco oil filter (3000 miles). When I tore the engine apart, the pistons slid out of the bores without the need for a ridge reamer and the bearings still looked good. I've found Mobil 1 definitely makes cold weather starting easier, but these cars aren't out then anyway.
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post #12 of 15 (permalink) Old Jun 8th, 05, 1:40 PM
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Bill
 
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Re: Oil weight for drag racing/street use

I think you might want to use an oil based on your application. Are you running a flat tappet cam or a roller? My engine builder advised me to use a 20W/50 with plenty of Zinc as I am running a pretty big solid flat tappet. Diesel oil is good in this application. If you are running a mild hydraulic roller, a light weight oil would be fine. But be aware, many of the well known synthetics of today do not have Zinc, so would not be as good in a flat tappet situation.
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post #13 of 15 (permalink) Old Jun 8th, 05, 4:12 PM
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Re: Oil weight for drag racing/street use

Royal Purple 10W30 makes good hp.

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post #14 of 15 (permalink) Old Jun 9th, 05, 12:18 AM
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Re: Oil weight for drag racing/street use

sorry, zinc, not sulfer.

71 z-28 454, 4 speed, 11.27@123mph
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post #15 of 15 (permalink) Old Jun 9th, 05, 10:44 AM
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Re: Oil weight for drag racing/street use

My dad and I have always run Valvoline 10w-40, I've switched to Royal Purple 10W-40 and he will do the same once his big block is built and broken in

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