Viscosity: Do you go by mfr spec or not?

[OneEyeJack]

Once you've made a change on your car for your driving conditions over a long period how would you ever know the difference, even with oil analysis, that is the difference if you had not made the change?

 

[spasm3]

Originally Posted By: Errtt
My DD fill cap specs 5w-20. I used 5w-20 during winter, but use 5w-30 non-winter, because I had both grades. Though the manufacturer states 5w-30 okay for towing, high temps etc. So since temps regularly runs triple digit temps, I already have the 5w-30 in use since spring - using PP currently.
Being the shear of 5w-20, maybe my 5w-30 shear may hold closer to the 5w-20 spec by end of OCI - I dunno. Engine is DI.
Other two vehicles I use what specs on the fill cap, one 5w-20 other 5w-30.


I do the same in the elantra ( 5w20 on the fill cap), its not DI but the manual supports me using 5w 20 in winter and 5w30 in the summer.

 

[ag_ghost]

The "new" cars in my sig specify 5W-30, though at least Ford nominally "back-spec'd" to 5W-20; never thought to check the Honda site. In any event, I've not deviated from 5W-30. They run great and with only 107k on the Accord and 167k on the Windstar, I seriously doubt engine failures will give cause to remove them from service. A good friend with up-to-date ASE certifications from whom I have learned much says I should run 15W-40 in the Ford. I respectfully ignore him.

Oh, I once inadvertently grabbed a bottle of 5W-20 when buying 5 quarts of Motorcraft oil for the Ford. I used it and the republic did not fall.

On my old Fords, I can't remember the nominal specs. The '63 Ford with 105K on its second motor has a little higher oil pressure at speed and at 190 degrees with 15W-40 and the Mustang seems to do just fine with 10W-30; its rebuilt 289 only has about 21K miles.
Kevin

 

[Garak]

Originally Posted By: Merkava_4
Engine feel any different with 0W-40 than 5W-30 ?

I notice no difference between the specified 5w-30 and the 5w-40 I'm using in mine, either. It certainly may be there and might be measurable under ideal circumstances, but it has not been noticeable.

 

[A_Harman]

I've never gone thinner than specified on the high-temp viscosity grade.

A couple of times I have gone up one high-temp viscosity grade.

Many times I have deviated on low-temp grades, always going lower.