Any downsides to thicker oil?

[StevieC]

I have heard a lot of talk about thicker oils lately and I have always been of the opinion that the grade called for should be used.

The only time I go against this rule is the 5w20 spec I usually use a 5w30 in the engines I own because it's usually just for CAFE standards and not really to the benefit of the engine.

But for an engine that calls for a 5w20 or 5w30 why use a 40 or 50 weight oil. What is the supposed benefit?

I just think that it creates a reduce flow situation through the engine by moving slower because it doesn't flow through the filter as well and because it's heavier to be pushed around.

Thoughts?

 

[buster]

You'll take a mpg hit usually. I'm thinking of moving to a 10w30 in the Honda. Most 30 grades are fuel efficient and have a low HT/HS of no more than 3.2. Volatility is also lower in a 10w grade generally speaking.

Putting anything beyond a 30 grade in my sluggish Honda makes it even worse. Honda runs best on a 20 grade. 30 is as high as I'll go.

 

[StevieC]

Probably because they run their fuel mixture right on the lean line so it would affect it large IMO.

I don't care about Fuel Economy as my fuel is paid for. Lucky me!

 

[HangerHarley]

Yeah.

I put a 10W-40 in a Honda once, made it feel Sluggish.

There was a thread some time ago about 10W-40 and Thicker in a Honda Civic, what ever became of that?

For me, a Honda 4 = 5W-30, as its likely to be an Accord or Civic.

Good cars.

Oh, and people also say a Thinner Oil makes their car "Feel as if it has more Power." As long as they are not sacrificing the Engine, how can that be?

 

[StevieC]

Not to get off-topic but with the 5w20 in my engine it feels a lot looser and more peppy in the butt-dyno. I have even gone back/forth to see and it is definitely more responsive.

 

[HangerHarley]

Originally Posted By: StevieC
Not to get off-topic but with the 5w20 in my engine it feels a lot looser and more peppy in the butt-dyno. I have even gone back/forth to see and it is definitely more responsive.



Car?

And do you mean back and forth between 5W-30?

 

[tig1]

I mentioned in the other thread that the bearing tolerance in my Duratechs is .0007-.0013. I'm sure Honda and others have that kind of clearance as well, so it seems lighter oils may be a benefit in this case. Also in 1978 when I first started using M1 it was 5-20 and didn't cause me any problems at all except a little more oil use.

 

[demarpaint]

Downsides to thicker oil. Off the top of my head, I'm sure there are more.

Possibly lower mpgs.
Higher than normal oil pressure.
Less oil flow.
More heat.
More drag.
Possible increase in wear during colder climates.
Could possibly shear more?

 

[fdcg27]

Hondas actually have a pretty rich fuel map.
Anyway, Honda used to spec much thicker oils than they now do, and the bearing clearances haven't changed much.
I am using 15W-50 in both of my Accords during warm weather, and it does make the engines both smoother and quieter.
Either car probably revs more quickly on the lighter oils I use during the winter.
Fuel consumption does not seem to increase noticeably, and I can tell you how much fuel each car has used on each tank for more than 100K each.
Asking what the benefit of thicker oil might be could be viewed the other way.
Any oil grade is thicker on a cold winter morning than the M1 15W-50 I'm using for the summer, so the startup flow argument isn't persausive.
An equally valid question might be to ask what benefits thinner grades have in warm weather.
During a northern winter, no question.
During a northern summer, how does a 5W-30 benefit the engine over a 15W-40?
Also, isn't higher HT/HS desirable in hot conditions?

 

[CourierDriver]

get a small aspirin bottle, put stp oil treatment in one

get another bottle and put 40wt oil in it, Place both in the freezer for one hr, then take them out,,and turn them upside down and just watch the show,,,,,u b the judge

 

[tenderloin]

Only experience of late for me is two of my Ford Explorers 4.0 SOHC spec'd for 5W-30.

With summer here and my companies work vehicles in the upper and lower deserts in 100+ temps, I decided to try M1 5W-40 in one of my companies Explorers...a 2005. My employee said he did not notice any difference, with the possible exception of the engine sounding more quiet.

I was heading to Lake Tahoe for a short summer trip/vacation so before I left I did a OC on my 08 Explorer.

It was quieter overall. No difference in start up noise. MPG on a trip from sea to desert to near 10,000 mountain pass roads and everything in between yielded about the same as last year with 5W-30. Normal cruising seemed the same. WOT seemed a tad lagging with the 5W-40

However since I have been back the past week or so..There seems to be a 1+ drop in MPG. Not scientific I know, just my observation and butt dyno.

 

[Steve S]

I have more important things to think about than the viscosity of oil . Unless the oil is way to thin or way to thick what is the big whop.

 

[aquariuscsm]

Originally Posted By: demarpaint
More drag.


That`s the only one I`ve experienced. My current fill definitely feels a lil on the thick side. 10W40 seems to me my car`s sweet spot.

 

[spasm3]

Originally Posted By: tig1
I mentioned in the other thread that the bearing tolerance in my Duratechs is .0007-.0013. I'm sure Honda and others have that kind of clearance as well, so it seems lighter oils may be a benefit in this case. Also in 1978 when I first started using M1 it was 5-20 and didn't cause me any problems at all except a little more oil use.


the same engine overseas is spec'ed for 5-30 or 5-40 oil

 

[StevieC]

My Santa Fe (2.7L V6) and yes 5w30 to 5w20

 

[StevieC]

My engine is spec'ed up to 20w50 depending on the temperature but seems to feel the best with 5w20 as stated on the oil cap and in the owners manual.

I don't get why thicker would be better...

 

[ThirdeYe]

I used 0W-40 in my 30-grade specified Honda engine. I thought it made it feel slightly sluggish but it could've been my imagination. It still hit redline no problem and could still chirp the tires.

 

[spasm3]

Originally Posted By: StevieC
My engine is spec'ed up to 20w50 depending on the temperature but seems to feel the best with 5w20 as stated on the oil cap and in the owners manual.

I don't get why thicker would be better...


depends on how you use your vehicle, if you are an easy driver light oil is fine. If you drive hard or tow then the heavier oils are going to be better. i find it interesting that the same engines overseas spec heavier oil the than the us. tends to make me think its all about cafe , not whats best for the vehicle.

 

[crazyoildude]

the downsides to thicker oil is lower mpg and slight horsepower loss (u can usually feel it) i always used the 5w20 in my modular engines until i hired a new engine rebuilder that told me to try 5w30 well i did but went back to 5w20 in under 100 miles... If the engine calls for 5w20 use it
The flow is better and the oil runs cooler

 

[CATERHAM]

I believe the old oil axiom applies;
"the oil should be as thin as possible and just as thick as necessary".

The biggest downside is the myth that you're providing more lubrication protection with a thicker oil.