Oil Recommendation - '56 Thunderbird

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Jul 29, 2002
Can anyone offer a recommendation for my father-in-laws newly rebuilt '56 T Bird 312 V-8? Should I be concerned with the issue of backward compatibility? I think a synthetic would be out given the fact the rear main seal on this engine is the old rope seal design. I'm afraid that would leak like a sieve? Thanks.
What driving conditions will the vehicle see (e.g. year round or part year use, miles per year, long or short trips, babied or driven hard, etc). Also, I lived in Charleston for a while but I don't remember, does it get below 40º very often?
It will be driven less than 1,200 miles per year. It sits in the garage sometimes for weeks on end. A lot of short trips, unless we have to endure another hurricane evac, in which case it'll get 10+ hours of stop and go driving just to travel 100 miles! This past winter in the Lowcountry we had several nights' temps dip into the low and mid 20's. Semper Fi.
M... My first choice if you weren't concerned about seal compatibility with an old seal design would be M1 15W50 especially if you could get it in the $18.88 5 qt jug at Wal-Mart, but a conventional oil that I think specs REALLY WELL against this motor is Pennzoil GT Performance (not racing) 20W50. I think this motor would love the stuff even if you have occasional temps in the 20s. Regards, Paul [ August 03, 2003, 11:15 PM: Message edited by: pscholte ]
Hi, I endorse the use of M1 15w-50 too. I had a '55 Customline as a young fella and after rebuilding its motor started it on 20w-50. It went well until I sold it a couple of years after to go on a world adventure! Great cars and good engines People with low use V8 water cooled Porsche' also endorse M1 15w-50 I use Shell Helix Ultra 15w-50 synthetic in mine Regards
I've used Mobil One 15W-50 in my original 1971 383 Chrysler for many years now (more than 50k). At this point I change at 6k or one year. I also wouldn't hesitate to used Mobil Delvac 5W-40, nor Schaeffers 15W-40. Amsoil, and others of highest quality would also do well in this general viscosity. I would recommend a search for the lowest-restriction, largest oil filter that would fit, and use FUEL POWER.
Why not go with Pennzoil Long Life 15w40? This oil would work out very well I think, just change it out once per year (just before the car goes away for winter storage)
I agree with Patman.Although it might be easier to find a 10w40 on a consistant basis,either one will work well.I have a 1970 Road Runner and I was using 30 wt Quaker State,but it's last change it got 10w40,and it gets changed 3x a year. I would suggest starting the car once a week regardless.
Originally posted by dickwells: IMHO any oil over 30 wt is way too thick for a newly rebuilt engine. A good petro 5W30 would be good to break it in on.
It depends on how the engine was put together though. Many rebuilders will use much looser clearances than what you'd see on a factory production engine. So even when that engine is fresh, it's clearances can probably handle a thicker oil than a 30wt, especially if it's an older design like in this car.
My recomendation would be Castrol GTX 10w-30 to start with. Then up the viscosity depending on how tight the engine is after a few thousand miles. My toyota has 250,000 trouble free miles with this oil in various weights. I think a synthetic is wasted in this application and dino is recomended by most mech. for an application that doesn't get many miles. Dino is suppose to cling better or longer to parts left sitting for long periods. This is what I use in the TR3 as it doesn't get driven as much as I would like. It has 25,000 on a rebuilt engine with GTX.
The original factory spec was probably 20W-20 with 10W-30 optional and straight 30 for hot weather. Conventional 10W-30 would be the safe choice. I used to run Pennzoil Long Life 30 in my '57 Chevy 283, now it gets 15W-40 Delo.
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