uh oh. I used the wrong oil.

[makken]

About 3 months ago I changed the oil in my car. I just realized that I accidentally used the oil for my sister's car instead of mine (she uses 5w20, i use 10w40, both mobil 1 synthetic). Now normally for the winter I wouldn't be too concerned; 0w20 is acceptable in harsh winter conditions according to my manual, but the past 2 months I have been doing long highway commutes in 100+ degree heat.

I just checked the oil level and it looks like i burnt through ~3qts (!!!) I normally go through 1qt between every oil change (~10k miles). Engine, for the most part seems fine; idle is a tad rougher than normal, but I can't tell any difference at speed. I'm actually getting a 2 mpg boost from the thinner oil.

I have a 200 mile drive ahead of me tomorrow temps have died down so that's kind of a relief. But I'm debating what I should do; I don't have the tools necessary for a full oil change on me right now so that's out of the question: mix the oil and top off with 10w40? top off with 5w20?

 

[Don Vito Corleone]

Why not just take it to a quickie oil change place? I understand you prefer to do it yourself, but unless you're driving something that requires exotic oil (which you're apparently not, since you yourself use Mobil 1) this seems like a safer bet than driving 200 more miles on the wrong oil (not that this is anything catastrophic anyway).

 

[thedarkwolf]

How much oil does your car hold? 3 quarts is a hell of a lot of oil. I'd just top it off with 10w40 since there can't be much oil left in there anyway. I'd be way more concerned with running the engine 3 quarts low than running the wrong viscosity.

 

[makken]

car holds about 7 qts. the oil level was completely off the dipstick. I added about 1/8 a qt of 5w20 and it was just touching the bottom of the dipstick. its ~2 qts from the bottom to the low line, another qt from low line to full line.

Why not just take it to a quickie oil change place? I understand you prefer to do it yourself, but unless you're driving something that requires exotic oil (which you're apparently not, since you yourself use Mobil 1) this seems like a safer bet than driving 200 more miles on the wrong oil (not that this is anything catastrophic anyway).

I'll be gone long before any of them open up in the morning, otherwise I probably would.

 

[saratoga172]

Top it off with 5w-20 and change when you get back or do the quickie change when you get where you're going. Don't mix the viscosities though. Especially with a 4:3 mixture. That would not be good.

 

[woodie1]

Top it off with the correct oil. The thinner oil will burn off and you can add more of the correct oil as needed.

 

[SparkyJJO]

Top it off with 5w-20 and change when you get back or do the quickie change when you get where you're going. Don't mix the viscosities though. Especially with a 4:3 mixture. That would not be good.

Mixing them doesn't hurt as not only are they both motor oil but even the same brand and type. If he has 4 quarts of 5w-20 and mixes in 3 quarts of 10w-40, the result will be about 7W-29 - hah sounds funny At least it would be closer to what he normally uses.

 

[saratoga172]

Mixing them doesn't hurt as not only are they both motor oil but even the same brand and type. If he has 4 quarts of 5w-20 and mixes in 3 quarts of 10w-40, the result will be about 7W-29 - hah sounds funny At least it would be closer to what he normally uses.

I always thought the two weights wouldn't quite mix right. Kind of like water and oil. The light would sit on top. Of course I'm going by what a couple bike dealership service techs told me. Maybe its a bike thing?

 

[Throckmorton]

What car is this?

 

[LTC8K6]

Just top it up with whatever you have handy, and change it out when you get back.

Check your oil level more often than once every three months...

What sort of car has a dipstick like that?

 

[arcenite]

Just dilute it with some water

 

[infoiltrator]

Oil "wt" rating depends on additive package, it is a performance rating rather than a strict "actual" rating.
IE, 5 wt is probably 5 wt oil base with additives to perform equivalent to 20 wt oil.
10 wt is probaby 10 wt with additives.
Add the 10-40, it wil mix and hopefully work close to a 30 wt oil.
Search for oil articles when you have time.

 

[DVad3r]

Top it off with whatever oil you want I'd use the 10 40.

 

[Zap]

I'd be way more concerned with running the engine 3 quarts low than running the wrong viscosity.

This.

I always thought the two weights wouldn't quite mix right. Kind of like water and oil. The light would sit on top.

But, it is oil and oil, not water and oil.

I'd say just top it off with what you normally use.

 

[hanoverphist]

i had an old beater truck that i would literally put whatever was cheapest in it. i ran that truck into the ground over a bunch of years, and 190k+ miles. there was more chance there was a mix of 30w and 20w-50 than anything else. keep the level in check and im sure youll be fine.

 

[SparkyJJO]

I always thought the two weights wouldn't quite mix right. Kind of like water and oil. The light would sit on top. Of course I'm going by what a couple bike dealership service techs told me. Maybe its a bike thing?

No, oil is oil. Add thin oil to thick oil and you get a medium oil. I'm not sure what those "techs" were thinking.

 

[Vetterin]

Two questions come to mind. 1st...what do you drive that takes 7 qts of 10W40 oil? The last car I used that in was my 71 442. 2nd...why don't you just drain the remaining oil and refill with 10W40 as all you would need is a wrench for the drain plug and a container. Keep the same filter and your good to go.

 

[bobdole369]

Nothing horrible has happened. slightly thinner oil won't hurt anything. Even the thin ass oil will still protect your motor. However as you've noted the thinner stuff WILL get through your rings and worn seals and whatnot. Just top off with 10w40 and keep checking till your next change and everyting irie.

 

[makken]

Nothing horrible has happened. slightly thinner oil won't hurt anything. Even the thin ass oil will still protect your motor. However as you've noted the thinner stuff WILL get through your rings and worn seals and whatnot. Just top off with 10w40 and keep checking till your next change and everyting irie.

Just got back from the trip. i topped it off with the 10w40 and didn't run into any issues. stopped by my parent's place on the way back and borrowed the jack so I swapped everything out and replaced it with 10w40. (its been ~7000 miles since my last change anyways)

Car is an E36 BMW with 212k miles; so I do expect some oil consumption. Still 3 qts over 2 months was pretty shocking to me.

 

[Throckmorton]

7000 miles on the wrong oil and 3 quarts short... How did your car survive??

 

[Gillbot]

I always thought the two weights wouldn't quite mix right. Kind of like water and oil. The light would sit on top. Of course I'm going by what a couple bike dealership service techs told me. Maybe its a bike thing?

lol

I mix mine on purpose. 1 qt 15w50 to 4-5qts of 10w30. the 10-30 runs on the thin side so the 15-50 help get it to where i want it to be.