Topic: Mixing Oils
in Forum: C3 Engines
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The last time I changed the oil in my '79 I used mostly 10W-30 but had to finish up with one quart of 10W-40. That's all I had in the garage.
Is this a big deal or not?
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I think since that is only 20% of the volume it will be OK. I like to stay with the same brand and not mix them unless absolutely necessary.

Kevin, for sure they should mix. And as for the time of the season, that 40w might be welcomed.

Thanks for the replies! A little piece of mind is all I was after.
A local car guy suggested that my witches brew could have caused me a big problem.
Well then, I may just let it accidentaly slip to him that I mixed up a concoction of Rotella, Syntec and even some STP!!! 'Nthen we'll really make him come unglued. 

I'm sure all the major oils have to meet the same code and can be mixed.
The only thing ya still don't want to mix these days is diesel fuel for regular fuel..........nnnot so good....................

Many, Many, Many years ago we had a loaner car at the Chevy dealer. Just one. A 72 Caprice. The new ones had not come in yet and the other ones were towed away one by one as they died. The last one burned a quart of oil every 100 miles.
The service manager wanted to know if it could go out for the last 300 miles it would ever need to go. The new loaners should be here on Monday, this was Friday. I told him no problem as long as they put oil in the car. He said it was an old couple, and they would not. Do what ever I could or had to, and make sure the car went 300 miles. He did not care if it blew up afterwards.
I brought it in. This was a very hot August, about 90 every day. I drained the oil. I put in 2 qts of 10W30. 2 quarts of 90W gear oil, and 1 qt of STP. The stuff was like creek mud.
The car started, ran quiet, quit smoking, and they went out the door. It came back Monday afternoon with 298 miles, and the dipstick showed full. The loaners did not come in Monday. The serivce manager put a customer in his demo. He drove the old loaner home and back. It now had a total of 302 miles from the installed blend.
At 10 am we needed a part for a customer waiting. The parts trucks were out, and no one to go get the part. He got a bit ticked and jumped in the old beast to go get the part.
The mistake. With a cold engine he opened the four barrel wide open in front of the dealership. Almost made it to the end. That sucker went BOOM. Literally. BOOM! As it rolled to a stop it left pieces and parts of the exploded engine and a trail of oil out on the street. The lot boys had to go out with a shovel to pick up parts and the oil dry they had to spread on Main St in Kent OH.
I had to laugh at him. He laughed later. He wanted 300 miles, he got 302. That's 2 bonus miles! 

The new loner/rentals did make it later that day. We got our chuckles over that for several years.
When I was a youngster my dad worked in a Esso station (that should date this) After they did oil changes I'd tip up the old METAL oil CANS with the big HOLE from the old filler SPOUT one by one to get the last drops. Then I'd use it in my mini bike motor. Its was my TIGER TAIL blend.

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Momence, IL - USA
Joined: 3/11/2008
Posts: 28
Vette(s): 1977 Corvette Coupe
Light Corvette Blue
all oils are compatable, diffrent weights, conventional, synthetic, high milage, all can be mixed together. Contrary to popular thought, all oils come from the same things, crude oil, pumped from the ground. The only diffrence is in the refining process. The syn oils come from cleaner more pure, non parrifin base stocks.
Hey Ken? What did you say you do for a living?



I am a Master Auto, Master Truck, Master Paint and Body, Alt Fuel, Advanced Engine Performance, Engine Block Machinist, Engine Assembly ASE Certified Technician.
I have written over 90 articles for trade magazines, and one News stand mag, with a second in the works. I hosted "Car Time" on WAKR radio in Akron Oh for 5 years. That was a call in talk show about cars 1 hour on Sat afternoon.
I have repaired cars and trucks for over 25 years, and now I teach others how to repair them at Ohio Technical College in Cleveland Oh. I also repair handicap scooters, power wheel chairs, and lifts for those units on Saturday, then work in an Autozone on Sunday.
Just a run down for those who don't know.
AND YES I DID THAT!!!!!!!!



He didn't want the old folks to need to add any oil. He got that. 

He wanted 300 miles. He got that. 

He wanted the part. He did not get that until later. 

He wanted a clear road. He changed that. 



BUT I DELIVERED ON HIS REQUEST!!!

AND THEN I LAUGHED A LOT!





You should always be careful what you ask for, you just might get it. 

Why should he complain about 2 bonus miles??? 

He was lucky. I considered two quarts of used oil, instead of the new stuff. 





And I remember proping up oil cans very well. The left over collected supplied the 64 Comet, and lubed door hinges etc. I actually collected gallons of the stuff.
in Forum: C3 Engines
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