Can thicker oil cause more wear?

Joined
Jun 1, 2015
Messages
1,309
Location
Arizona
Thin is in folks let’s drain them heavy ass oils out before summer hits . Let the 20wt flow like cafe wants you to . You may get a little more wear but it won’t stop your motor to getting to 300K 🙃
I wont disagree that it is possible to get to 200k using 0w-20 but IMO a lot less likely. For the minute % difference in mpg 0-20 promises I will still lean toward a lower chance of failure in the long run.
 
Joined
Aug 5, 2002
Messages
19,004
Location
Silicon Valley
For engine with oil controlled stuff like variable valve timing / lift if the oil is too think it may skew the intake / exhaust valve timing. In those engine I wouldn't use something way too thick. Otherwise like others said it is really just cold start.
 
Joined
Jan 14, 2015
Messages
2,231
Location
missouri
Does a higher viscosity oil drain off parts faster. I have a wheelchair ramp van that usually sits a week or 2 weeks between starts. It is specified for 5W20. I have NO consumption, 5 K changes look almost new, but it is a year. would a 5W30 or a 10W30 have better start protection after sitting.
 
Joined
Dec 6, 2019
Messages
283
Location
South
someone mentioned variable valve timing already. Some engines have jets that spray piston skirts to assist with cooling. yes CAFE has caused the use of thinner oils however it seems that modern engines with VVT and piston skirt cooling have also been engineered around the use of thinner oil. The particular engine design should be the deciding factor in thick vs thin debates.
 
Joined
Dec 10, 2013
Messages
732
Location
Kuala Lumpur ,Malaysia
I knew a guy who used 20W-50 and 10W-60 in winter in the UK. He spun bearings twice. he thought 20W-50 wasn't thick enough the first time and he went to 10W-60.
I am on 5W40 all year in the tropics and no failure, on the same engine.
 
Joined
Apr 7, 2019
Messages
279
Location
VA
I once ran 15W50 in my old 97 Honda Civic. It speced 5W30. I remember it felt sluggish, lol.
I used Castrol Syntec 5w40 in my 97 once and could tell a big difference with the engine response compared to the 5w30. I've found that by just letting the engine deal with it that it will eventually shear or basically thin out overtime or maybe you just get used to the slower feel of it. I remember one time I added 1qt of QS HM 10w40 and could tell the difference, I believe the other 2.7 qts would've most likely been 5w30 at the time.

I don't see where a thicker oil can really hurt anything but only on the newer engines where they have all this new technology with all those sensors and even having the computer involved but all that aside if we're talking a basic mpfi engine or something older then no problem and the thicker oil can only help with protection but possibly could hurt the mpg's a bit due to the thicker oil being more viscous which would be harder to pump and create more drag on the moving parts inside the engine mostly being the reciprocating assembly. The thicker oil could help with burn off if you have an oil burner, also could help with leaks as it wouldn't seep out as easily.
 
Joined
Aug 5, 2002
Messages
19,004
Location
Silicon Valley
Does a higher viscosity oil drain off parts faster. I have a wheelchair ramp van that usually sits a week or 2 weeks between starts. It is specified for 5W20. I have NO consumption, 5 K changes look almost new, but it is a year. would a 5W30 or a 10W30 have better start protection after sitting.
Sitting 1-2 weeks will not matter, but sitting 1-2 hours yes, 30 would cling to the parts longer than 20.
 
Joined
May 17, 2021
Messages
727
Location
open range
While I agree that one step thicker won't hurt, I'm still convinced you're safe using whatever your manual recommends. Comparing UOAs, I don't see any downsides running thin oils in engines where the manufacturer recommends those thin oils. Quite the contrary those UOAs tend to read excellent.

Btw, groundhog day?
 
Joined
May 18, 2021
Messages
302
Location
central europe
with newer cars you have exhaust piping in the head, and more complicated cooling system. engine will get warm faster.
cold wear should be minimal.
 
Joined
Sep 10, 2005
Messages
4,995
Location
Massachusetts
with newer cars you have exhaust piping in the head, and more complicated cooling system. engine will get warm faster.
cold wear should be minimal.

I disagree. Review the coolant lines in a carbureted '85 Honda Civic (or many other vehicles of the time) and you'll find modern engines are much more simplified. There are no vacuum operated doors to divert exhaust heat to the air filter or hundreds of feet of emissions vacuum hose. Engines warm up faster due to superior engine management.
 
Joined
Aug 25, 2018
Messages
2,114
Location
South Carolina
A lot of older engines had exhaust crossovers in the intake manifolds to provide quick heat to the carb and coolant. Spark timing has a major effect on how quickly an engine warms up. If you look at modern EFI tables, they keep the spark timing retarded during warmup, sometimes as low as single digits advance. Then once warmed up, the idle spark timing will jump into the 20+ degree range. Older engines accomplished this with ported manifold vacuum that keep timing retarded to warm up quicker. They lacked the ability to change the timing at specific temperatures though.

I personally don't care about the coolant temp. I care about the oil temp. The hotter the oil, the higher the specific heat, the greater the evaporation of water and fuel dilution (and other contaminants), the greater the reactivity of additives, and better the oil works overall. The oil won't heat up much just idling. It needs load and friction. Drive the darn thing.

Here's a few pictures from a dyno test. Notice the oil temp vs GPM oil flow at a steady pump rpm.

189211454_4253346001350622_8172146222543901288_n.jpg

187128552_4253346281350594_6122243044746996392_n.jpg

189328655_4253346454683910_2259791924565257937_n.jpg
 
Last edited:
Joined
Jun 15, 2010
Messages
2,086
I disagree. Review the coolant lines in a carbureted '85 Honda Civic (or many other vehicles of the time) and you'll find modern engines are much more simplified. There are no vacuum operated doors to divert exhaust heat to the air filter or hundreds of feet of emissions vacuum hose. Engines warm up faster due to superior engine management.
Actually newer vehicles are starting to have very complex cooling systems. Gone are the traditional engine coolant thermostats, the most advanced cooling systems today use a thermostat module. These modules can alter coolant flow to multiple areas of the engine all in the name of efficiency.
 
Joined
Sep 10, 2010
Messages
3,228
Location
GA.
Thicker oil should provide better moft and thicker film and I assume less chance of contact and wear especially in summer heat and with high revving engines or high load or high rpm or hot running turbo engines.

I always use one grade over the manufacturer recommendation (to neutralize cafe) or at least use a higher hths (a3/b4) of the recommended oil if possible. Meaning I never use xW-20 or lower. I prefer a solid 30 or a high hths 30 and/or a regular 40. However I pay good attention to the W rating as @ZeeOSix mentioned. In general, I prefer narrow spread oils but have been violating my rule lately by using some Euro 0W-40 for the summer.
A number of Hyundai / Kia owners manuals indicate : "5W20 , 5W30 or 10W30 may be used . The selection should be based on the ambient temperatures you expect the car to be driven during the next OCI" . For wife's 2.0L PFI Kia engine and my 2.4L GDI engine 5W20 is what is stamped on the oil cap but according to the owners manual going up to 5W30 or 10W30 is perfectly fine . *Perhaps when potential wear is discussed - what shape may the oil grade you choose be in say 3,000 ~ 5,000 miles into an OCI (i.e. shearing , reduced film thickness) ? If you are on the fence on the topic - what about choosing a "thin" 5W30 like PPPP (9.8 cSt) over a 5W20 synthetic (8.4 ~ 8.6 cSt) ? While most xW30 synthetic oils are 10.6 ~ 12 cSt the PPPP 5W30 at 9.8 cSt may be your answer .
 
Top