Thinnest oil I can safely use in my TBI 5.5L?

[Skunksmash]

I've been reading up on synthetic oil on Bobistheoilguy.co m. It seems that any full synthetic oil will slowly clean the inside of your engine. Some better than others however. The best full synthetic right now is Redline, which even eats varnish off. So I'm going to run that for a little while just to help clean up my old 5.7L TBI engine. Anyway, the thinner, the more quicker it can clean, apparently. So I was just wondering what the thinnest oil I can safely use in my 5.7L is. 5w20 perhaps?

[bigchevyc30]

idk if it works or not but my dad said when you change oil in a vehicle you bought or one you have and think needs to have the insides clean to fill it with diesel for where oil goes and run it for 10 min not to warm up the motor or anything just to get it running through as it will clean the oil glop out of the passages. im not sure if this work he says he did it back in the day and is going to have me do it on my 366 that we bought and he says not to put the new filter on till u have emtied out the diesel

[zieg85]

My dad used to do it about once a year in his work car.  Never had an issue.

[topp]

You can also add 1 qrt of tranny fluid, run for 10 minutes, then drain and replace oil and filter....
You can add Seafoam to the oil, and then run it for a while, then drain and replace oil and filter....

[bigchevyc30]

though for me im going with diesel he told me to put 2 gallons in since i have a 10qt oil capacity

[Skunksmash]

I know about all those methods but I prefer to use a slow and steady method, rather than all at once. So does anyone know what the thinnest oil I can safely use is?

[topp]

I know about all those methods but I prefer to use a slow and steady method, rather than all at once. So does anyone know what the thinnest oil I can safely use is?

"thinest" is defined by your location and climate, How often you run your truck, what conditions you run it under and many other factors....

[Skunksmash]

The punishing Texas heat is my climate. I don't drive the truck daily. I probly only a couple days a week. As for conditions I run it under, I pretty much baby the truck. I don't rag on it at all cause its just an old truck. No point in raggin' on something that was never meant to be fast lol.

[bigchevyc30]

i agree with you on the trucks not built to go fast since i put in the new motor in my truck its only seen the interstate 1 and it was only a 3 miles on that. my old motor went out cause i always went on the interstate when i head into town. but like you now i dont hotrod and things like that since it still dont have any good fuel mileage

[Skunksmash]

Guess I'll just try 5w30

[nativetexan]

If you don't drive it that often, and if its an older engine, I wouldn't worry about thinning out your oil. Just run what you have been running to keep your seals tight.

[slammed79]

Also, if you switch to full synthetic it is a pita to go back. As I understand it, you need to do an engine flush before switching back to conventional.

Just heresay really, but someone might have more info on this.