SpeedyV6

Since I only run Mobil 1 oil in my car I've decided to extend the oil change interval from 7,500 miles to 10,000 miles. Anyway, I checked my dipstick and it was 1/2 way between full and empty so I figured I may as well add half a quart. Normally I follow Honda's recommendation and only use 5W-20 weight oil. But considering that the temperatures in Texas is normally between 90 - 105 degrees this time of year I was thinking about topping it off with straight 30 weight motor oil.

Can adding SAE -30 oil to 5W-20 harm the engine in any way?


PS: Michael Wan where are you?

teranfon

[QUOTE=SpeedyV6]Since I only run Mobil 1 oil in my car I've decided to extend the oil change interval from 7,500 miles to 10,000 miles. Anyway, I checked my dipstick and it was 1/2 way between full and empty so I figured I may as well add half a quart. Normally I follow Honda's recommendation and only use 5W-20 weight oil. But considering that the temperatures in Texas is normally between 90 - 105 degrees this time of year I was thinking about topping it off with straight 30 weight motor oil.

Can adding SAE -30 oil to 5W-20 harm the engine in any way?

Hi SpeedyV6

I am honestly not too sure if you will do damage or not. Perhaps a more qualified member can give you more of a definitive answer. But it seems to me that you want to add a single grade oil (30) to a multi-grade oil (5W-20). To the best of my knowledge the 5W designation refers to cold weather viscosity and the second number 20 refers to warm weather viscosity. Multi-grade oils such as 5W-20 have polymers added to the oil which allows for the multi-grade designation. Now the 30 weight you refer to also a viscosity rating, that of course being 30. It would appear to me, and again I'm certainly not a professional, that you will have two different oils of two different viscosities (when warm) in your crankcase. I would expect this, although not harmful, not to be entirely advantageous. You have to remember that the engine in your car is rather recent, and manufacturers now build motors with very close tolerances. I'm sure they specify a multi-grade oil with 5W for initial start up protection and the following 20 designation when warm for a reason. If it was an emergency I would say do it, but would personally leave it and change the oil a little sooner.

Sorry I couldn't be more helpful.

Terry

SodaLuvr

I don't see the point to adding a SAE30 to your crankcase. It would make little or no difference at all in protection given the small amount that you're adding. The only disadvantage that I can see would be reducing low temperature performance of your current 5w-20 fill.

The "thicker is better" theory is outdated. While a higher grade of oil may provide a thicker oil film, there's more to oil lubricity and film strength than viscosity alone, as the oil's additive package plays a very important part.

SpeedyV6

I was thinking that the 5W-20 might be a little thin for Texas summers. That's the only grade that Honda recommends - perhaps for the sake of simplicity, fuel economy, and low emissions - but it seems to be so much hotter here than it is everywhere else that I figured a higher viscosity oil might be better for the summer. Plus I drive fairly long distances so low temperature / cold engine protection is less of an issue for me.

It surprises me that, even though most automakers no longer recommend different grades of oil or high visocosity oil, anytime you pull into a convenience store or a gas staion the two most common grades of oil that almost everyone has are 10-30 (which is perhaps the most widely recommended grade) and SAE-30 which virtually no automaker specifies.

As for additives i'm not too worried. I only have 2000 miles to go before my next oil change.

iTimmy

The heat in Texas is not enough to think about changing grade oils, mixing seems kind of like a waste. The 5W20 has less to do with the temperature that the vehicle operates at and more to do with the tolerances the engine was built to. Honda engine's are built very tight, bearing tolerance is not large enough for a higher viscosity oil, long term the thicker oil will damage things, in addition decrease fuel economy as soon as its added.

The fact that texas is 120 and NY is only 90 isn't going to make a differnece, it will be to operating temp. in a few minutes in the 200 degree range, that's the joy of a multi viscosity oil like 5w20 in a tight engine it(viscosity) varies based on temp as required.

In other words, just use 5w20 if that's what the manufacturer says.

SodaLuvr

I think half of the "internet experts" who claim that Automakers have not fully tested 5w20s are complete donkeys.

Automakers test their recommendations (oil, coolant, etc) under the worse case senario for validation testing.

If you do not think they've tested it in TX in the middle of summer, I don't know where you guys are coming from.

I know, for one, that Death Valley and Phoenix are popular spots for automakers to test their vehicles in the summer. 120F, 130F is not uncommon in that neck of the woods.

Same with cold start testing, engines are left overnight in -40 in Northern Canada with no block heater. They are started, run for 1 min, then driven at full throttle immediately afterwards.

iTimmy

Now where is Michael Wan, I am sure he has some insight

crazymjb

^Thats Wans new name(no red so I figured no sarcasm)

Mike

SpeedyV6

That's interesting.

iTimmy

I haven't been around for 2-3 weeks, I guess I missed a few things