Mixing oil (I know it's generally bad, but...)

[kraxxus]

I goofed. Brainfart @ advance auto. Bought 10w-30. 2006 Scion tC takes 5w-30. I found backups of 5w-30 at my house though and I had enough for an oil change. Drained my oil. Then noticed 1 of the bottles was 5w-20 (gf's car). Long story short I refused to put the 10-30 in cuz it's winter time. I have 112.4oz of 5w-30 and 22oz of 5w-20 in my car. (Total 4.2 quarts-Yes I did the math). Everything is synthetic since 10k miles. 110k miles now.Normal OCI is 4k miles. Since the starting viscosity is unaltered do I even have anything to worry about other than barely faster oil burn off? Yes I am taking 10-30 back for exchange, incase someone gives me valid reason to change oil again sooooon.

 

[HTSS_TR]

No problem at all, actually it will help a little in cold start when the temperature dips to below zero in Jan-Feb.

 

[rjacket]

Don't worry about it.

 

[ueberooo]

You should be fine for the winter, running with 20% 20 weight and mostly 30 weight mix. like someone above said, it might even be beneficial. Change your oil before April, or add a bottle of STP or other similar addv, or top off with 15w40 or so when warmer weather comes around.

 

[kraxxus]

Ok awesome thanks guys that makes sense. Actually I'll just be back to normal 5w-30 synthetic before spring. 4k OCI won't even get me 3 months @ 17k/year.

 

[gathermewool]

Run your normal interval. I'd recommend against adding anything to thicken it up, ESPECIALLY something like STP. If it does burn off and you do have to top off, then add the spec'd weight, 5W-30. Also, your thread title about mixing oils being bad is not correct. There's nothing wrong with mixing oils. I'm surprised others haven't chimed in about their high mileage cars run exclusively on franken-mixes. Also, why not run longer intervals? 17k/year, you must have a high percentage of highway miles. I could imagine changing my oil every three months. If I could find an oil that would allow me to go a full year I'd jump at it. While my car and long intervals don't go hand-in-hand, you shouldn't have any issues going at LEAST 6 months.

 

[CharBaby]

Originally Posted By: kraxxus

I goofed. Brainfart @ advance auto. Bought 10w-30. 2006 Scion tC takes 5w-30. I found backups of 5w-30 at my house though and I had enough for an oil change. Drained my oil. Then noticed 1 of the bottles was 5w-20 (gf's car). Long story short I refused to put the 10-30 in cuz it's winter time. I have 112.4oz of 5w-30 and 22oz of 5w-20 in my car. (Total 4.2 quarts-Yes I did the math). Everything is synthetic since 10k miles. 110k miles now.Normal OCI is 4k miles. Since the starting viscosity is unaltered do I even have anything to worry about other than barely faster oil burn off? Yes I am taking 10-30 back for exchange, incase someone gives me valid reason to change oil again sooooon.

I have been mixing oils for 40 years and there is nothing wrong with it. I have never destroyed an engine yet and I have put on over 300K miles on some of these engines...4 cylinders at that! The 2.4 L engine in your tC is a fine engine and the 10W30 mix you have in it right now is perfectly fine even for winter. Maybe not optimal but, fine just the same. And being synthetic, the flow capabilities are even better in the cold than regular motor oil which is all alot of folks are using anyway even in colder climates than Pittsburgh As others have mentioned, you are a perfect candidate for extendes oil change intervals(OCI's) expecially since you are using synthetic oil. Many folk here are running normal conventional oils for greater than 5,000 miles. Your 17K miles/year is ideal for extended OCI's. Oh I don't know; more than 5,000 miles though!