Used 5w20 instead of 5w30 per manual

I live in AZ currently it’s over 100F. I accidently used 5w20 instead of 5w30. should I drain it out and replace with 5W30 before the next oil change? What about the filter, can I wait to replace that until the next oil change?

I the car still under warranty? If so, I might drain it and replace the oil. No need to replace the filter.


I’m no mechanic, but I’m 99% sure that going to a lower-viscosity oil in hotter conditions is the wrong way to go. If it was me, I’d drain the 5W-20 (but I wouldn’t bother with removing and draining the filter - not that much oil) and add the 5W-30. The 5W-20 probably won’t have a big impact, but for the cost, why take the chance?

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Does your temp gauge read hotter when it is 60f vs 95f? Cars cooling system controls engine temp. Not outside air. Drain 20w and put in 30w.

It seems that answering this person is difficult : Are we talking about a complete oil change - or just adding oil to the vehicle - what year is vehicle - what does the manual list as oil requirements.

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If the oil is 100% synthetic the 0W20 will be OK. But if the car is new and under warranty, I would drain it just to be sure. The best oil, of course is 0W30 synthetic that will withstand the highest temperature and also heavy loads in case you are towing a trailer.

Irlandes may chime and mention that in Mexico they put 20W50 in most cars.

Modern, however, cars rely on the engine oil to optimise the valve timing, so that you should not deviate from the manufacturer’s specification. That’s one reason for the 0W designation, it allows the valves to function properly during cold starts. A thick 20W50 will screw up the system.

What year is your car? I know for my 1999 Honda Civic, the original recommendation was 5W30. 5W20 was just about unheard of in 1999. In recent years Honda has said 5W20, and has recommended that retroactively, so I now use that in my Honda.

Start by analyzing what your owners manual and/or service guide book say. Then consider the possibility that those are giving you outdated info.

10-30 vs 5-30 vs 0-30 is the same when hot
0-20 vs 5-20 is the same flow
5-20 vs 5-30 is not the same

At very low temperatures, a 0W20 flows better than a 5W20. However, in most areas there is little difference.

At very high temperatures, a 0W30 Synthetic has better film strength than a typical 5W30 mineral oil.
The reason for these discrepancies is the laboratory test for high and low only covers a range of 100 degrees C. Where I live, winter starting temperatures are way lower than the test and summer driving while towing a trailer results in extremely high temperatures. So, synthetic oil, has that wider viscosity range or a much higher Viscosity Index.

I would check the oil regularly at each gas fill up and not worry about it. My independent shop put 5W-20 instead of 5W-30 in the 2006 Uplander I owned. Although it was in the winter, we took several long trips in the van. I didn’t have to add any oil. I did make certain that 5W-30 was installed at the next oil change. The Uplander now belongs to my son, and is going strong at 200,000 miles and has had no major engine work.
I would bet that more damage is done to an engine by oil that is too thick rather than too thin. Most of the wear occurs at startup when the engine is cold. Thicker oil doesn’t circulate as fast to the bearings and cylinder walls.

It was a complete oil change 2 weeks ago. Full synthetic. 85k miles. Just bought the wrong type by mistake. I’m just going to drain it and fill it with 5w30 instead. Manual list using 5w30.

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Yeah that would make me feel better on a TSX for the $25 worth of oil. However, the manual specs 0-20 for my V6 Acura regardless of outside temps and that’s what I use. Likewise I’ve never understood the the outside temp issue since the engine will operate at 220 degrees regardless. Cold starts are a little different since the oil will be the same as the ambient temperature.

Cold starting has always been the number one consideration in Canada and the USA. Now we have a need for fuel economy and 0W20 is now the preferred oil by manufacturers. The other consideration, as stated in my previous post, is the oil acts as a hydraulic fluid to actuate the valve timing.

Synthetic oil has a very low “pour point” which is exactly what that means. A -48 degree C rating means the car will have oil flowing in pretty well all temperatures encountered except the Alaska North Slope!

“Borderline Pumping Ability” is another measure of cold weather performance. Again, a -46C is a good measure. At 0F, a typical 10W30 mineral oil behaves like very sticky molasses and has no lubricating ability. Before we had thin multi-grade oils, we all had engine block heater in our area, since a really cold start could burn out you bearings through lack of lubrication.