Just chunk a gallon of Castrol 20-50 and a quart of Marvel Mystery oil in the crankcase, add a quart of ATF to the next tank of gas, push that Black Sabbath 8 track in, turn it up to eleven and send it!!! We'll fix it tomorrow...
I would read the chart as: Any of the listed oils are acceptable within the listed temperature range, however, not all of the oils are ideal within the given temperature range. At the lower end of a given range, the thinner oils listed are closer to ideal while at the upper end of the given range, the thicker oils listed are closer to ideal.
I remember seeing this in the manual in the 80's, I always ran 20w50 in my car that I knew was going to be pounded on back then, and the commuter got 10w40. Interesting in 2003 new regal with 3.8 came delivered in Detroit and the oil cap said 5w30 only while my parents took delivery same car near Tampa and the oil cap said 10w30 only. So the question and joke always was if I'm driving from Detroit to Tampa do I stop near Atlanta to change the oil? It's going to be 95 here today and 92 there today. Winter a different story on the temps obviously.
My question is what has allowed the use of thinner oils in modern engines. We know what's driving it - MPG but it also equates to increased HP. The 3.8 Doug references above is a perfect example - Same engine had been around for 40 years but now can use a thinner oil. Earlier in this thread there's talk of oils and bearings. Seems to me it's better/tighter tolerances not allowing as much leak down but idk. If so, we could seemingly run the thinner oil in older iron. Everything now I think calls for synthetic so as @Max Damage said, if they don't thin as much cold maybe oils have something to do with it as well (0W-20 oils are now common). I suppose comparing an older 3.8's engine specs/bearings/etc. to a 2003 might yield some insight.
Exacting manufacturing and tolerances enable tighter clearances. That allows the use of thinner oils. I use 10W-30 synthetic oil in my 470, and my oil pressures are great. Have a look at the recommended bearing clearances in my 1998 Riviera 3800,
That's what I figured but I suspect there's more to it at the OE level. I assume a big one is rod side clearance & also lifter bores & lifters themselves. Could one run 5W-20 in a properly machined old engine? What would be the HP diff.?
I would think so, but not in our BBB. I think the crank is so huge. Not sure you would want to tighten the clearances that much unless you intended to run it at lower RPM. <4500.
Max has it right here, the purpose of the chart is to inform the owner of what oil to use, to insure low temp oil flow and lubrication during cold start, in reference to the outside temp. Once the engine has reached thermostat temp, any of the oils listed will work fine, in a new engine, regardless of the ambient temp. As was stated, if the cooling system is functioning properly, actual engine temp should vary no more than 10* or so above thermostat set temp. What the factory did not want is folks starting the thing up with 10-40 in it, when it's -10F in January. That is the purpose of that chart, I would read nothing else into it. Now, what a particular 52 year old engine wants for oil weight may be a completely different thing, but that's another topic entirely. JW
Just remember 20W-50 is not 50 weight oil. It is just 20W with viscosity improvers to help it from thinning out under heat. It's really just some extra protection when oil is hot. Unfortunately the viscosity improvers break down over time and the oil becomes 20W-40....then 20W-30 and eventually back to a 20w. Sorry my grandfather was a chemist who worked in the oil and filter industry. Learned a few things from him.....
Not really.. I have always used 5-30 in the winter... when it gets that cold, a block heater is the key to getting it started at all, and gettin it running without the scary noises.. I recall my first daily driver.. 73 455 Centurion with 150K miles on it.. no block heater in that one, and below zero you could hear every main bearing hammer for the first few seconds when it was that cold out. But I was young and dumb back then, and just needed it to run.. JW
In my opinion, the impact that electronic fuel injection has had on the longevity of newer engines can not be overstated. The more precise air fuel ratios and better atomization of gasoline that is provided by fuel injection has greatly reduced wash down of cylinder bores and the dilution of oil in the crankcase. Prior to fuel injection, most engines were worn out by 75K miles even with oil changes every 3500 miles. Today 6,000 to 10,000 miles is the recommended oil change interval, and engines with 300K miles barely show wear to the cylinder walls.
Yes, modern FI does make a difference, but I think 75K is a little low. My first Buick, a 1972 Skylark, had 250,000 miles on it when I had to junk it. The body rusted out before the engine gave out. It still ran like a top at the point. I kept it tuned, and it got 2500 mile oil changes.
Yeah gotta agree with Larry. I had numerous 150K plus motors with carbs. The thing is alot of folks didn't start carbed motors correctly but ANYONE can start modern cars. Just turn the key. People used to flood by pumping too much or have a stuck choke or bad tuneup. Tuneups are now pretty much a thing of the past. But yes oil changes were more important due to fuel dilution and motors had more blowby (tended to use more oil). Also older cars didn't have rev limiters. You could do alot of damage in a short amount of time.....ask me how I know......
A lot of carbed engines died young because, by 75k or so, they were often in the hands of an owner who wouldn’t fix a carburetor that didn’t crank easily or had vacuum leaks and was washing the cylinder walls with raw gas. That same owner likely was neglecting oil changes and buying cheap gas, too. Long term owners who kept up maintenance and repairs got long term success. Thise who ignored the hard starts didn’t. Patrick
Back in my farming days there was an 2000ish F150 that the farm bought for the hired men to drive. It had about 100k on it and rotted badly. They changed the oil and put 15-40 in it since they buy that in bulk. The first day it was -20° the oil pressure blew the cam phasers and timing chain tensioners. It threw a fist full of codes and the timing chain was pretty noisy but still ran ok. It ran for years like that.
That's the exception to the rule. I remember growing up, when a car hit 100k, it was done. Likely needed a valve job and it was smoking blue. You basically gave it away.
