Can thicker oil cause damage?

[fdcg27]

I have been using thicker than spec oils in some of our cars for the past few years.
The van was the first victim, having seen Quaker State Synthetic 5W-50 and Syntec 5W-50, as well as Mobil 1 Extended Performance 15W-50, a blend of 2 qts GTX 20W-50 + 3 qts GTX 5W-20, a well as Tection Extra 15w40.
The Havoline DS 10W-40 in it currently is probably too close to spec to count.
The '97 Accord was on Tection 15w40 for one run last summer, and is now on Mobil 1 Extended Performance 15W-50. It has seen Pennzoil Conventional 10w40.
The '99 Accord is now on the same Mobil 1 Extended Performance 15W-50 it saw last summer. It has also seen Pennzoil Conventional 10w40.
I have never noted any ill effects with the thicker oil, which I only use during warm weather. There doesn't seem to be much loss of fuel economy, either.
Has anyone seen any actual damage caused by the use of thicker than spec oil in warm weather?

 

[Panzerman]

Well, I ve had no problems anytime I tried a thicker oil, but I have read alot of Hypotheticals on here from your starter wont be able to turn the engine over and your engine will knock for the first 15 minutes of start-up till the oil gets warm enough to move. Mostly propaganda put out by manual followers, too skeered to try the thick stuff.

 

[tig1]

50 years ago 10w40 conventional would cause severe lifter clatter in extreme cold. That's just one reason engines didn't last as long then as they do now.

 

[Roy Gutfinski]

Generally, no, as long as there is sufficient flow at start up. The only disadvantage, even after warming up, is decreased gas mileage due to drag of the more viscous oil on moving surfaces in the engine. It will, however, decrease engine wear generally.

 

[Bigsyke]

I think the oil film strength should be the most important, and ive read on here that some 5w20's have a thicker film strength than the thicker oil grades.

 

[sprintman]

No.

 

[mechtech2]

You state that you only use thicker oil in warm weather.
Obviously, you are already somewhat aware of the problems of too thick oil.

Engine damage? Flow is greatly educed on cold/cool start ups to remote parts of the engine -the farthest from the pump.
Variable cam systems often don't like thicker oil. Lifter buckets can drag and cause rough idling or other anomalies until warmed up.

 

[vxcalais]

Originally Posted By: Bigsyke
I think the oil film strength should be the most important, and ive read on here that some 5w20's have a thicker film strength than the thicker oil grades.


Redlines HTHS 5w20 is higher or equal to the next grade up. Going too thin, or too thick will damage your car. I have run a 10w30 which burnt oil to a 25w60 with no dramas but did feel some lag. I sit around the 5w40 to 10w50 mark now depending on what i can get.

 

[fdcg27]

Well, I don't think you'd want anything thicker than a 10W-XX in winter here, and I avoid even that, prefering a OW or 5w30 for winter. They're all thicker oils at really cold temperatures.

 

[ET16]

I doubt damage, but I could imagine you losing some horsepower and mpg with this regimen.

 

[aquariuscsm]

Originally Posted By: sprintman
No.


^^I`ll second that.........*no*

 

[twigdog]

Just what are remote parts of the engine?

 

[Gary Allan]

There won't be any damage, imo. That is unless a Canadian or norther plains state engine is damaged by any oil @ -25 or lower. Even when they achieve full flow, the visc that they're pumping is off the visc chart. They appear to live long lives. Now if there is some visc sensitivity to cam phasing apparatus and whatnot, then there may be some delay in their functionality, but ..again, the same crowd should experience that with even the thinnest 0w-20 with a starting temp of -30F for a good bit into the driving cycle. That's in comparison to some 70F person using 40-70 or whatever.

You will be pumping glue longer. The amount you perceive it in fuel economy will mostly depend on your trip length.

On the other end of the equation, you're not doing your engine any favors using heavier oil than spec'd unless you're in some really unique situation.

Naturally those who do this tend to think that their situation is unique ..even if it's mundane and commonplace ..or otherwise with the normal envelope of competence of the spec'd fluid. For the run of the mill daily driver, he/she is wasting their time thinking that they're doing their engine any favor pumping heavier oil.

 

[mechtech2]

Originally Posted By: twigdog
Just what are remote parts of the engine?


Like I said - the farthest from the pump. Oil goes through passages and through/around bearing areas.
The actual farthest point would be cam bearing/valvetrain on common OHC engines.
Lubro Moly did a test of light and medium oil concerning flow to all parts of the engine on start up. [this was not selling their product - it was just a test]
The results were more than significant.
I also note a much longer time for oil pressure gauges and lights to activate when using thick oil vs. thin, when the gauge is on the end of the cam.

I am a believer in that there is no oil too thin at start up.

 

[Art_Vandelay]

Originally Posted By: mechtech2

I am a believer in that there is no oil too thin at start up.


No doubt in the world that is true.

 

[Steve S]

Originally Posted By: twigdog
Just what are remote parts of the engine?
Rear bumper

 

[aquariuscsm]

Those "nooks and crannies"

 

[zjones]

Yes...Sure Can, So can thinner oil.

I have a 5.3 Chev V8 and Mfg recommend 5w30...I run 5w30, go figure.

There are all kinds of oil reasons to run different viscosity so spend some time to study that.

30-40 years ago engines were made with wide clearance and somewhat inferior material and techniques There were exceptions of course but these days it's pretty much all good stuff.

Let's look at say the big end rod bearings in your engine...40 yrs ago clearance say .120 in. Today .30 in. I'm not gonna get into a debate about oil but here's a hard fact you can't escape.

Today's engines require thinner oil because clearances are much closer and oil has to create a film barrier to properly lubricate...too thick of an oil WILL NOT WORK properly in these newer engines. The thicker oil will NEVER create the proper film barrier for example on big end rod bearings at any temp...start up or operating temp or sunny days or even when it's raining, whatever...it won't happen if it's too thick for the clearance or the galley that feeds the bearing.

Might want to heed mfg engineer's advice in this area. I personally cannot think of one single benefit running thicker viscosity oil outside mfg specs for it's normal service life

 

[OVERKILL]

You are confusing tolerance with clearance.

Let's delve into your post a little.

For a small block Windsor engine (which have been run on 20w50 by racers for eons), the range of clearances and their respective tolerances are as follows:

Critical Tolerances
Main bearing clearance 0.0025-0.0030 inch (0.0027)
Rod bearing clearance 0.0020-0.0030 inch (0.0026)
Rod side clearance 0.0100-0.0200-inch (0.0140)
Crank endplay 0.0004-0.0008-inch (0.0006)

Let us fast-forward 30 years to the Modular engine:

Main Bearings 0.00098-0.00197 inch
Rod Bearings 0.0010629-0.0027165 inch
Rod side clearance 0.005-0.019 inch
Crank endplay 0.003-0.015 inch


So, the antique Windsor has a tighter end-play spec, as well as a tighter tolerance for rod bearing clearances, and side clearance. The Modular has tighter mains.

 

[zjones]

Thank you OVERK1ll Edited for clarity