quickie about mileage and weights....

[Johnny248]

In a real world situation, why would a 0w30 or 5w30 oil get better fuel mileage than a straight 30w oil if the viscosity at 100 is the same on all three weights?

I read that an engine running SSO (amsoil 0w30) would get a little better fuel economy than the same engine running ACD (10w30/30). They both have a viscosity of 10.5 at 100. I would think this would be the normal viscosity of the oil when you are actually drive and using the vehicle.

How much driving does your vehicle do while the oil is at it's colder, higher viscosity? It really takes engine oil that long to warm up to operating temperature that you would see a noticeable difference in mileage?

 

[Dominic]

Yes -- once warm, they will all be the same approximate viscosity. The mileage burden as well as wear burden occurs during the first 20 minutes the engine runs (warm-up) until the oil is at normal operating temperature and viscosity.

**Viscosity is not the only factor that controls fuel efficiency.

http://www.bobistheoilguy.com/motor-oil-101/

 

[jorton]

Right. How many minutes are your daily drives. Mine is 45 one way so the oil is warmed up only half the time.

Honestly it's not as bad as that. The afternoon drive home starts in a pre-heated vehicle!

 

[Johnny248]

It really takes 20min for engine oil to reach temp? that seems like a long time. Especially if you are running at hwy speeds or something

 

[yaris0128]

Originally Posted By: Johnny248
It really takes 20min for engine oil to reach temp? that seems like a long time. Especially if you are running at hwy speeds or something
I have a hard time believing that myself. 20 minutes? I know my Honda temp gauge gets up to running temp in less than that. If that were true then my entire trip to work and back my oil wouldnt have gotten up to temp going at highway speed the entire 17 miles.

 

[mopar_monkey]

it has nothing to do with your temp gauge or coolant temp, it takes some time for heat to fully transfer through out the engine and to the engine oil.

 

[yaris0128]

Originally Posted By: mopar_monkey
it has nothing to do with your temp gauge or coolant temp, it takes some time for heat to fully transfer through out the engine and to the engine oil.
but 20 minutes?

 

[TFB1]

Originally Posted By: yaris0128
Originally Posted By: mopar_monkey
it has nothing to do with your temp gauge or coolant temp, it takes some time for heat to fully transfer through out the engine and to the engine oil.
but 20 minutes?

Unless it very cold outside or the vehicle has a oil cooler, figure approx 10-12 min on the average engine... Another way is add five minutes after coolant temp is up to operating, this will allow the oil temp to catch up...

I changed the oil in my '07 Grand Marquis recently... From a cold start it ran maybe five minutes till the coolant temp was almost to the point of the thermostat opening(I made sure to cut it off before full operating temp)... When I removed the drain plug, oil was hot enough to burn your fingers if not careful...

 

[mechtech2]

Warm up will vary greatly due to ambient temps, and the load on the engine.
From 5 min to 30+ min.

 

[30valve]

Both my Audi's have oil temp gauges. Generally it takes 8+ min of driving just to get the needle to move off the minimum 150F reading on the gauge. Coolant temp gauge is already to normal temp by this time.

It takes another 5-10 min to reach normal operating oil temp on the gauge. Basically I generally see 13-20 min to get oil to full temp and this is in the summer. Winter adds about another 5 minutes.

I should also add that both crankcase capacities are about 7 qts, so quite a bit of oil to warm.

 

[fdcg27]

In a real world situation, I doubt you'd see any difference in fuel economy among these oils.
You know which one you'd prefer for a Detroit winter, but for summer driving, I don't think you'd see any difference in fuel economy in actual use.

 

[demarpaint]

Originally Posted By: yaris0128
Originally Posted By: mopar_monkey
it has nothing to do with your temp gauge or coolant temp, it takes some time for heat to fully transfer through out the engine and to the engine oil.
but 20 minutes?


Depends on outside temps, engine design, and the materials used in making the engine. In the winter it can take even longer for an engine to reach operating temps. 20 minutes is a fair average.

 

[Johnny248]

Originally Posted By: fdcg27
In a real world situation, I doubt you'd see any difference in fuel economy among these oils.
You know which one you'd prefer for a Detroit winter, but for summer driving, I don't think you'd see any difference in fuel economy in actual use.



Right...The car I am using it in sees use from about april-ish to November maybe. It goes in storage for the winter, never sees snow. For some reason I like the idea of not having any vii's in the oil.

 

[30valve]

IIRC GC 0w30 has little to no vii's in it so may fit the bill and still leave you with a multi-weight oil.

 

[CATERHAM]

Even in the summer, running a straight grade (low VI) oil can be very problematic unless you never turn the engine off like taxi and police cars.
For most of us short trips are often the norm, and low VI oils do significantly reduce overall fuel economy; hence the development by the OEMs of higher and higher VI oils not to mention the other lubrication advantages.

A VI of 170 is the norm for a synthetic oil today.
M1 0W-40 is the factory fill in many European cars and it has a 185 VI.
But for the ultimate in fuel economy you'd have to go with the Toyota Brand 0W-20 with it's 214 VI. This 20wt oil has about as much in common with a dino 5W-20 in terms of start-up viscosity as the typical 5W-20 does with a 10W-40.

I don't care all that much about fuel economy but I like very high VI oils because I want the lightest oil possible (for a given HTHS viscosity) on start-up even on a 90F summer day.
Why? So that I can use high rev's as soon as possible without the oil pump going into by-pass mode. That can take 10 or 15 minutes even with a light high VI 20wt oil.

It's one reason why M1 0W-40 is often used as a race oil. It's high VI means it's relatively light when starting a race engine at the track. A lengthy warm up period is often not possible before extracting maximum performance.

 

[mopar_monkey]

Originally Posted By: yaris0128
Originally Posted By: mopar_monkey
it has nothing to do with your temp gauge or coolant temp, it takes some time for heat to fully transfer through out the engine and to the engine oil.
but 20 minutes?

i'd say up to 20 min, that is defiantly on the high end.

 

[CATERHAM]

Originally Posted By: mopar_monkey
Originally Posted By: yaris0128
Originally Posted By: mopar_monkey
it has nothing to do with your temp gauge or coolant temp, it takes some time for heat to fully transfer through out the engine and to the engine oil.
but 20 minutes?

i'd say up to 20 min, that is defiantly on the high end.

It very much depends on the vehicle and the ambient temperature on how long it will take an engine oil to get up to say 100C.
Engines with oil/coolant heat exchangers along with shrouded engine sumps will heat up the engine oil the fastest.
But if your engine has an exposed aluminum sump and no heat exchanger it may never get the oil up to even a low normal operating temp' of 80C during the winter months.