I was told by an old timer at my local parts store that I should only use straight weight 30 non detergent oil in my 240 inline six. True ? if not what would you all recommend? He claims the detergent oil will hurt my engine. BTY I hope to register the old girl next week and head down for an alignment and inspection sticker and back into service she goes. Fingers crossed

 

I ran 10W40 in the 65 300 six that I had twenty years ago...did that for years and it was fine.

I'm running 10W30 in my current 66 240 six and it seems to be fine. (for what it's worth, I'm using 10W30 because I happened to have a case of it in my garage when I bought the 66)

and oh yeah....the whole oil thing.....brace yourself....discussing oil preferences is akin to discussing religion or politics.....people get testy and zealous about it.

 

My engine rebuilder suggested the same thing, but only for the break-in period.

 

When I was a kid , we would never dream of using non-detergent oil. Sometimes, I used it when I was broke ($.19/quart at the time) and I was driving my usual mosquito fogger. It was the general consensus that this stuff was to be avoided. I never really knew why.

Now I just googled it. Interesting.

Motor Oil Myths and Facts

 

I don't want to start a controversy at all. I just never heard of this and he seemed adamant about it. I see where people get locked into their opinions. I just don't want to screw up this 46 years young engine.

 

Thanks hollygreenman,I got some reading to do!

 

When I was in high school back in the 60s I worked for my dad who was an engine rebuilder. I can recall some motors comming into the shop so sludged up you could not hardly tell the internal workings of the inside of the motor. Im pretty sure he would tell me this was due to poor oil change habits and non detergent oil. Seems to me if you sludged up a motor like that and then went with a detergent based oil it was told to me you stood a good chance of plugging up the oil galleys in the motor if they werent already. Might be what that old bird was refering to.

 

I have to agree about Oil being a religious thing. I am hard core about 2 things. I think you should choose an oil and stick with it. I have had bad experiences with switching oils. (I once bought a used car and put a high detergent oil in an engine that the PO ran Pennz 10/40 in. It cleaned out all the old paraphin, and the engine started knocking. Went back to Pennz, and it stopped. I drove that car for 100k 200k including the PO mileage.) I really like synthetic oils in a new engine. I would find out what oil has been run in the truck if possible, and run that. If you can't find out then I would run any of the standards. Quaker State, Pennz, Valvoline.

On the subject of multi grades vs straight grades, I have always heard that multi grades are for places like Colorado where the Temps vary widely. If you are in a southern climate that is more stable then straight grades are okay.

 

Modern oils have a much lower level of Parrifin Wax Base and do not coke up as much. The Detergents are to keep the engine oil from coking.

10/40 will run fine in the 240. Avoid anything less than 10/30 as the machined internal tolerances for the oils like 5W15 are a lot tighter.

All new rebuilds should run straight 30 with a ZINC additive for break in of the cam and lifters. Rotella 30W and other deisel spec oils have this. If they do not GM sells an over the counter additive.

All modern gaskets are manufactured to take in to account the new oil formulas. (chances are there are no existing gaskets still on the engine)

Garbz

 

I think I'll go with the detergent oil and let the consensus here rule. What has been stated here makes sense and I have no idea what has been in it in the past. It's got just shy of 70,000 original miles and I don't think this engine's been gone into. Thanks for the help it's an interesting subject I never thought much about. I'll use the straight 30 for the oil bath filter

 

Sounds like a good plan.

On my new vehicles, I run dinosaur oil in the weight that the manufacturer recommends for the first 20K miles or so, then I switch to Royal Purple.

I did that with a Chevy Silverado, and just recently sold it.....going strong at 324,000 miles.

 

I would be hesitant to use straight 30 on the oil bath air cleaner your engine has to pull the air through the oil to breathe the thicker the oil the harder this is to do. the shop manual recomends 30w above 32 degrees and 20 w below 32 degrees. it also recomends using 10w-30 untill the temp gets below -10 degrees f

 

Hey Jazzmaffy have you pulled the valve cover to see exactly what you are dealing with? You can tell alot about how that motor was treated by taking a look there first.

 

Not sure what you mean by coking. I have not heard that term before as to how it relates to internal combustion motors. Could you please enlighten myself and possibly others who also may not have heard this before . Thanks Im going to google now to see what I can come up with.

 

I had an old '66 Plymouth Valiant with a slant six. It burned oil and had blowby. I ran non-detergent oil in the beast, because I didn't want anything blowing up at that stage. The engine still had plenty of power - those slant's were good motors. Cheap oil in a cheap car. If your engine is not burning oil, then you're prolly ok to run detergent oil.