M1 15W-50 in 302

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2,231
Location
SE MI
I've tried thinner oils in my 1981 302 w/ 98k miles but they all foul the spark plugs. I suspect "leakage" caused by worn rings or rings w/ clearances designed for thicker oil. Ford called for 10W-40 back in 1981. THe use of xW-30 and xW-30 synthetics would foul the plugs in 30 days or more. I've replaced the valve stem seals already but the use of xW-30 would eventually cause a no start condition. A few ppl suggested I tried synthetic 15W-50 in the motor year round. Any ideas on this?
 

Patman

Staff member
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21,990
Location
Oakville, Ontario
From what I understand the 302 uses pretty loose clearances, so this might be one rare case where a thick 50wt oil might work out pretty well. I say to go for it.
 

Al

Messages
19,206
Location
Elizabethtown, Pa
If that is the Chevy engine-I had one and it always used about a quart every 1500 miles. Naturally in those days I used a 40 wt. ('69 Camaro). Don't recall any plugs failing.
 
Messages
453
Location
Galveston, TX
quote:
Originally posted by metroplex: I've tried thinner oils in my 1981 302 w/ 98k miles but they all foul the spark plugs. I suspect "leakage" caused by worn rings or rings w/ clearances designed for thicker oil. Ford called for 10W-40 back in 1981. THe use of xW-30 and xW-30 synthetics would foul the plugs in 30 days or more. I've replaced the valve stem seals already but the use of xW-30 would eventually cause a no start condition. A few ppl suggested I tried synthetic 15W-50 in the motor year round. Any ideas on this?
I had a 1981 year 351 v-8 Ford once. The whole time I had it, I never had to look at the plugs. I just never had oil-related problems*. My oil? Castrol mineral single-grade HD-30. [* The electrical problems were a killer though. G** Damned Fords!!!!!! :-)]
 

metroplex

Thread starter
Messages
2,231
Location
SE MI
[Smile] My 302 V8 doesn't use oil but it did blow out blue smoke once when I did a warm start (carb'd car, so you're supposed to hold the gas a little and crank) so I replaced the valve stem seals. My definite guess is the ring clearance is causing the oil fouling problem w/ the plugs - again it doesn't do it with 10W-40 but it does it w/ 5w-30, 10W-30, and the synthetic xW-30s.
 
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