I try to do right by my car. But this time, I mis-remembered the weight of oil it ‘wants’. The manual calls for 10W-30 in most driving conditions, 5w-30 if it’s going to driven in sub zero conditions. Somehow that translated to 10W-30 in the winter, 10W-40 in the summer in my head. So, weighing the likely difference, vs. walking the two miles to the auto store to exchange the oil. I went ahead and poured in the 10W-40. (Of course I hadn’t double checked until I had drained the old oil.) The engine is a 1.3L 4 cyl. in a Chev. Metro with 86,000 mi. on it. It’ll be driven in the Phoenix heat, we’re already having 100+ degree days.
What can I expect if I drive the next 5000 mi with a slightly too heavy oil in my engine?
You live in Phoenix? I think you’re probably OK. Oil weights have been “downsized” in part to improve fuel economy and ease of starting in cold weather.
Shouldn’t be a problem unless you have something semi-exotic like a new Hemi with MDS that needs really light oil - 5w10.
I remember a time when it was pretty much normal to go up a viscosity once an engine was past 75,000 miles or so to compensate for normal wear and increased oil consumption.
I doubt there will be any measurable difference over the course of 5,000 miles. Leave it in.
This is not to say that viscosity never matters. Consistently using a non-recommended oil can have negative effects, especially if the first number is too high (e.g., 10W-30 where 5W-30 is called for) or the second number is too low (e.g. 20W-20 where 20W-50 is called for). But in your particular climate, I wouldn’t be surprised if the 10W-40 protects as well as, or even better than, the 10W-30. It certainly won’t be a problem for the duration of one oil change.
Thanks for the responses so far, they pretty much reflect my thinking on the matter.
I’m gonna find out if I can even tell the difference, but it might tempt me to do the next change at 3000, instead of 5000. I change at 5k even though most of my driving is in the city. We can go there, though that’s nearly GD territory. I know the manual recommens 5k intervals only if the majority of the driving is long distance highway type travel that stresses the engine less than stop and go.
The Hemi is semi-exotic? Sweet, I had no idea. But I’m glad I saw this, I’m getting ready to do my first oil change, and I probably would have used 5w30.
Had you gone down in oil viscosity you’d have a problem. For heavy loads and high heat, many manufactures jack up the recomended number by 10 points. The more heat the runnier the oil. Winter in Wisconsin would show you why you don’t want 10W. You wouldn’t turn over the engine at 10F or lower temps.
Threadjack! Recently I found my oil was all burned up (happens all the time in my car) and I filled it up with some 10W-30 that was labeled “TRUCK/SUV FORMULA” or somesuch. What the heck is that? Just marketing? Does it have something in it that could damage my non-truck engine?
Nah. There is talk in some circles that “racing oils” are better for older push-rod/lifter style engines. Diesel rated oils are recommended, even for gasoline engines of this type, supposedly because of the continuing addition of extreme pressure lubricants like zinc. The converse however is not true - using a non-diesel certified oil in a diesel engine. Were you to go into an auto parts store and pick out a gallon of motor oil at random, the odds are it would be OK for use in a gasoline engine.
I’ve come back to report that I imagine I can feel some difference in how the engine feels, but it’s not bad at all. Just heavier, more solid, somehow. Prolly in my mind.
