Running a thicker oil than spec harmful?

[dsmith41]

There was a thread on BITOG a few months ago about using a heavier grade oil and if that was harmful. I was searching for that thread today because I couldn't remember the consensus as to whether or not it would harm anything. I found nothing. So I'll ask again...

If your car calls for a XX-20 and you put in an XX-30, will that damage your engine long-term? What about putting XX-40 in an engine spec'ed for XX-30? Obviously, fuel economy will suffer, but are there any other negatives?

 

[Pablo]

Which engine?

 

[toyota62]

Next grade up should be ok.Stay thin as possible and as engine getting older switch to thicker grades.

 

[Bill in Utah]

You know the bottom line is in your engine the way you operate it where you live we don't know.

And until you take a few down the long road and run the exactly the same with different oils the answer will not be known for sure.

With that said, I'd run what they recommended because we know that they DID test the engines up and down the road and had acceptable results. I'm sure that they also tried other oils and found something to be less so they went with worked.

The reasons for NOT using a thicker oil could be MPG, engine life, noise on start-up, lack of oil on cold start ups or many other things.

The reasons for not using a thinner oil could be engine life/wear, noise on start-up, lack of oil when warm or many other things.


Clear as mud....

Where I live I see quite a few test fleets going down the interstate wrapped so you don't know what they are. They stop and get gas and I sometimes talk to them. They drive a TON of miles and then look at the results. I'd bet a few of the vehicles has some oil and the others have other oil. Some run this part and the other runs another. Nissan seems to really TEST the [censored] out here because I see them the most.

Take care, Bill

 

[friendly_jacek]

Originally Posted By: dsmith41


If your car calls for a XX-20 and you put in an XX-30, will that damage your engine long-term? What about putting XX-40 in an engine spec'ed for XX-30?


The answer is: no way!
One grade difference up has no impact and many times dino oil will thick up one grade up at the end of long OCI and that is considered OK. On the other hand, VVI shear down or fuel contamination will lower viscosity one grade down and that is also considered OK. If you drive very fast or in a very hot climate, you will actually decrease wear with one grade up.

 

[Audi Junkie]

5w-20 is optimal for winter and/or short trips.

 

[dsmith41]

Originally Posted By: Pablo
Which engine?


Well in my case, Ford 4.0 SOHC

Thanks to everyone for the quick replies.

 

[BuickGN]

I'll put it this way, I would be much more comfortable going up a grade than going down a grade. As long as it's appropriate for your climate and usage there won't be a problem.

 

[crinkles]

5w-30 to 20w-50 is specced for my 2AZ-FE camry. I can use all of them since it never freezes where I am

 

[sprintman]

No

 

[vxcalais]

I am going from 15w40 to 10w60 Castrol Edge. I have even used a 25w60 and my engine still made it to 230,000k's so far.

 

[bullwinkle]

The main problem with thicker oil is cold weather pumpability-makes the engine harder to crank over & start, & slower to get oil pressure & flow to critical distant areas such as cam bearings & up to the underside of pistons & rings. It's harder on fuel economy as well. It probably won't hurt anything to jump up ONE grade, but a little extra warmup time or a pan heater in winter wouldn't be a bad idea.

 

[demarpaint]

Going up one grade thicker an oil won't be a problem, but why not use what the mfg suggested? Save the thicker oil for if/when you have a problem that requires it. Like Bill in Utah said the mfg has tested the engine and determined what works best for it. If they give choices of different grades match the grade to the climate and work load of the engine and call it a day. That's what I do.

 

[jorton]

10w-40 will be thin enough for cross counrty use, but 10w-30 will be better than 10w-40 for short trip use where your drives are under 40 minutes.

 

[fdcg27]

Quite often , you can get a super closeout deal on oil and you may happen to find such a deal on a fairly thick oil.
Now, for the way I use a car (one start followed by 25 miles of driving, with some minor errands through the day), I doubt that a thicker than recommended oil is going to cause any problems during the warmer months of the year.
For the above reasons, I just did about 6K with my '99 Accord on M1 EP 15W-50.
Also, as some have/will point out, much thicker oils are recommended for the same engine in markets outside the US, where 5W-30 is the recommended fill.
There is a member here who uses M1 15W-50 (not EP) in everything all the time. He lives in a climate only slightly warmer than mine.

 

[river_rat]

Originally Posted By: BuickGN
I'll put it this way, I would be much more comfortable going up a grade than going down a grade. As long as it's appropriate for your climate and usage there won't be a problem.

Well said

 

[Jeff3126]

At my work we have a fleet of F-150s, 250s, 350s with 4.6, 5.4, 6.0, and 7.3, plus some diesel construction equipment. We run mobil 15-40 in everything, even in chainsaws as bar lube. Been that way for years, no probs.

 

[Minou]

Originally Posted By: Jeff3126
At my work we have a fleet of F-150s, 250s, 350s with 4.6, 5.4, 6.0, and 7.3, plus some diesel construction equipment. We run mobil 15-40 in everything, even in chainsaws as bar lube. Been that way for years, no probs.


Maybe in South Florida but it wouldn't cut it up here.

 

[Steve S]

Originally Posted By: jorton
10w-40 will be thin enough for cross counrty use, but 10w-30 will be better than 10w-40 for short trip use where your drives are under 40 minutes.
What if the drives are 43 minutes?

 

[JohnBrowning]

No it is not harmful. WHat is harmful is running an oil too thick for ambient tempatures!!! This is what cause's turned beariing, starved top end etc.......So if you lived in the North or North east of N. America running 25W70 during a hard winter would be beyond stupid. on the other hand running 0W20 in a Duramax Diesel or a Ford Porwer storke an attempting to pull at max load through the Appalachian or the Rockies would be equally stupid. You have to match the oil to the engine and the envirnoment not either or. People in AMerica have gotten lazy because most of their owners manuals for years have only had one oil recomendation. Notice I said recomendation as well and not One oil Gospel or absolute truth based in fact..........