tanderson2002us

I changed over to Rotella Synthetic last fall and just did my spring oil change with Mobile 1 Diesel Syntheic. There is an obvious difference in warm up time (slower) and overall temp. with this product. Has anyone else noticed this? I also run about a quart over the full line on the dip stick.

Thanks,

Tom

SIXSLUG

I'd say you reduced friction a little with the Synthetic, which would make less heat.

Are you reading the factory temp gauge?

tanderson2002us

Yes....it has not reached the "middle" since I changed the oil, only about 3/8 on the gauge.

dkenny

sound like something else changed.
I run the rotella synthetic T6..I still see around 190 on the gauge.

now what changed? no clue.

-dkenny

SIXSLUG

My gasser sees slightly higher oil pressure at standard operating temps with synthetic vs regular 5w40. Supposedly the viscosity in the synthetic is more stable thru the temps and doesn't thin out as much.

I still say less friction produces less heat. However, relying on the stock temp gauge isn't all that accurate.

Keep your eye on it over the duration of this change and see what it does.

rickf

Engine temp is dictated by the thermostat, I would say to replace it.

Rick

tanderson2002us

Thanks everyone!! Yes....It does run about 1/2 way between 140F and 190F. I will look at replacing the thermostat. and see if that changes anything.


Happy Memorial Day!!

Tom

KATOOM

I agree. Even though synthetic will potentially lower any friction drag which could reduce engine load, reducing engine temperature to a point, the thermostat will still dictate how hot the engine runs.

tanderson2002us

Thank you!!!

HOHN

The slightly higher oil pressure you're seeing has almost nothing to do with syn vs non-syn.

Viscosities are assigned to the oil based on thickness near operating temp (212F for the spec). With a 190 stat, your oil is running about 220F. Can you see the difference in 8F viscosity, never mind the difference in 8F between a syn and non-syn? No.

A 40wt oil is a range of viscosities. It's quire possible that the syn is just in the higher end of the range. Not because it's syn, but because that's how they blended it. There are other non syn 40wts which would probably show you even higher OP.

At low temps, you should expect to see lower average oil pressure with the syn, and that's a good thing.

When an engine is cold, the oil pressure is super high because there's very little flow. The oil is thick, and all the orifices (bearings, PCNs, etc) become far more restrictive. As the oil thins, you get more oil flow because of the lower restriction, and this lower restriction shows up as lower oil pressure.

hth.

tanderson2002us

New $22.00 T-stat did the trick.....running right at 190F.

Thanks,

Tom

RowJ

Probably not a Cummins, at that price.
Do yourself a favor next time (which may not that far down the road).
Go with a Cummins T-stat. It's one factory part that seems to make a serious difference in dependability and performance.

Glad the solved your mystery!

RJ

SIXSLUG

That makes sense HOHN. It seems to use less between changes with the synthetic, but that may just be remembering it wrong.

It does show higher on the factory gauge though.