Oil Weight and Fuel Consumption at Warm-Up

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Would my fuel consumption improve in the first 15 km if I went from a 5W-30 (PU or PP being used depending on what's available) to 0W-30? My car barely warms up to operating temperatures during my daily commute. I have oil temperature and pressure gauges. Not surprisingly, my pressure drops to middle of the gauge's range when the oil is truly warmed up. At start up, my pressure is on the high side, which is also normal during a warm up.

Thanks,
Andrew
 
You may wish to try a 0w20 or 5w20 PP or PU if the engine is in good shape - otherwise you need a bicycle or a moped or electric scooter.:)

What's the car?
 
There isn't much difference between 0w/5w at mild temps, only when really cold -15 to -40 degrees F. I don't know celcius off top of head.

Actually something like GC, which is a 0w30, but on the heavier end, is most likely thicker down low negatives.

But if thats a turbo you get better heat protection and longer drain intervals with cold performance and cleaner engine if you believe SOPUS
 
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My car: 2013 Ford Focus ST.

Climate: Pacific North-West (Metro Vancouver, BC, Canada). Typical morning temps these days are around 5C. Winters are pretty mild, but hover around 0C.

I have to drop off my kid at the daycare on the way to work.

Thanks!
 
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Supposedly the reason to go to 5w-30 vs 10w-30 was indeed better fuel economy at cold start. IIRC, GM wrote papers justifying this.

Its a reasonable thing. While we know that we can see fractions to single digit percentage changes in MPGs in controlled conditions changing by a few cSt at operating temperatures (e.g. 20 vs 30 vs 40 wt), the differences at cold start could possibly be bigger when the oils are fully cold. The issue is that notionally the vehicle doesnt spend a lot of time when the oil is fully cold/thick, but for city drivers that may be a bad assumption. Further, getting oil to flow faster in the engine is always a good thing

So there really is no downside, assuming shear stability and no VII issues.

The issue really is that like most engineering, there are tradeoffs and diminishing returns. Going from a straight weight or even a 10w to a 5w- likely has a benefit, but it may be getting less and less at reasonable temperatures and use.

From an engineering analysis POV, you WILL see an MPG improvement assuming the oil is actually less viscous at the startup temperatures of interest. Whether youll see it or not is another question...
 
I would think that any 0W-30 might give minuscule fuel economy advantages. But the way you can really save a little cash using a 0W-30, is that by definition, 0W will be a synthetic. Because your car has a turbo, extended drains may not be your best bet, because the oil will be put through the ringer on the turbo and you may be prone to fuel dilution. Even still, running it to 7500 with a quality synthetic probably wouldn't be a problem. Mobil 1 AFE 0W-30 would be what I could put it in for its price and availability (though in Canada, I may be wrong) but really any API 0W-30 will do!
 
Originally Posted By: jhskier25
I would think that any 0W-30 might give minuscule fuel economy advantages. But the way you can really save a little cash using a 0W-30, is that by definition, 0W will be a synthetic. Because your car has a turbo, extended drains may not be your best bet, because the oil will be put through the ringer on the turbo and you may be prone to fuel dilution. Even still, running it to 7500 with a quality synthetic probably wouldn't be a problem. Mobil 1 AFE 0W-30 would be what I could put it in for its price and availability (though in Canada, I may be wrong) but really any API 0W-30 will do!


For some reason Mobil 1 AFE 0W30 isn't available in Canada. Op's best bet might be Caterham's blend (60% TGMO 40% either M1 0W40 or Mobil Delvac ESP 0W40)
 
Originally Posted By: richport29
Originally Posted By: jhskier25
I would think that any 0W-30 might give minuscule fuel economy advantages. But the way you can really save a little cash using a 0W-30, is that by definition, 0W will be a synthetic. Because your car has a turbo, extended drains may not be your best bet, because the oil will be put through the ringer on the turbo and you may be prone to fuel dilution. Even still, running it to 7500 with a quality synthetic probably wouldn't be a problem. Mobil 1 AFE 0W-30 would be what I could put it in for its price and availability (though in Canada, I may be wrong) but really any API 0W-30 will do!


For some reason Mobil 1 AFE 0W30 isn't available in Canada. Op's best bet might be Caterham's blend (60% TGMO 40% either M1 0W40 or Mobil Delvac ESP 0W40)


Petro-Canada 0w-30 is another option.
 
You'll see something like a 2% better fuel economy going from a "30" to a "20", the zero or 5w number doesn't matter much here.
 
Given that the OP is talking warm-up, the popular position on the board is that for a given 30, with the same HTHS, the 0W-30 will provide better economy during warm-up.

It's logical, real, and really probably imeasurable...still real, and worthy of consideration if the prices are the same, and the HTHS required for protection is there all OCI.

Dropping a grade will provide more, ala FetchFar's estimate...as long as the OP is certain he has his bases covered for protection.
 
Does Ford specify 20-weight in the owner's manual for the Focus ST? If so, 0w20 will give you the best chance to save fuel during warmup.

Most 0w30's available today are disappointing in low temperature viscosity. For instance at 0C, M1 0w30 will have a viscosity of 524 cSt, and M1 5w30 will have a viscosity of 490 cSt.

On the other hand, M1 0w20 has a viscosity of 324 cSt @ 0C.
 
Originally Posted By: ajwan
.... My car barely warms up to operating temperatures during my daily commute. I have oil temperature and pressure gauges. ...


What ajwan goes thru is the same thing I experience. My wifes car is speced for a 5w-30 but I fearlessly use a 0w-20 (high-moly Mazda-Idemitsu) because she only goes 4 miles each way to work and back. The oil never gets thin enough. The 0w-20 probably gets in the tight spaces in a cold/cool engine better.
 
As others have mentioned the switch to a 0W-30 will only result in an increase in fuel consumption if the oil is actually lighter on start-up than a particular 5W-30, which means an lower combination of HTHSV and VI.
There are no very high VI 0W-30's on the market but if you're not concerned about warranty explanations you can blend your own using the reasonably priced TGMO 0W-20 and either M1 0W-40 or Delvac 1 ESP 0W-40.

Since you have oil gauges you're in the fortunate position to be able to fine tune your operational viscosity to how you drive your car. If you know what the factory OP test spec' is at elevated rev's, you may be able to run TGMO 0W-20 straight without testing that spec' if your oil doesn't get too hot. If not then through some experimentation determine how much 0W-40 you'll need to add to maintain the minimum required OP when the oil is as at normal operation temp's and also when the oil is as hot as it ever gets when you're hammering it.
 
Originally Posted By: CATERHAM
If you know what the factory OP test spec' is at elevated rev's, you may be able to run TGMO 0W-20 straight without testing that spec' if your oil doesn't get too hot.


Do you have an official PDS for TGMO? I need accurate values for KV40, KV100, density & HTHS. I've got a handy spreadsheet here at work that calculates oil properties at all temperatures between 0 and 150C and want to play around with different blend numbers of TGMO with M1 0w40.
 
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