Really? Why?
Synthetic increases MPG in a COLD engine.
- Thread starter batterycar
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Don't really have data to say one way or another to say for positive. But I would think that there would be very little difference bc the viscosity graphs of conventional 5W-30 and syn 5-30 oil are about the same. After the oil ages-and the conventional oil thickens with respect to a syn oil you might see a small difference. The difference is more pronounced in the "Urban cycle"
I have a SAE report (2002-01-3530) that shows tht fule economy of a 20W-50 oil vs a 5W-30 oil.
The improvement in efficiency (milage)of the 5W-30 vs the 20W-50 is about 5% for the Urban cycle and 3% for the Highway cycle. So based on that I would think the improvement for two oils of the same grade (even with one synthetic) would be almost nothing.
I have a SAE report (2002-01-3530) that shows tht fule economy of a 20W-50 oil vs a 5W-30 oil.
The improvement in efficiency (milage)of the 5W-30 vs the 20W-50 is about 5% for the Urban cycle and 3% for the Highway cycle. So based on that I would think the improvement for two oils of the same grade (even with one synthetic) would be almost nothing.
I partially agree with Al - the difference may be to small to measure. But there would be a difference.
To answer the "why" it's simply the viscosity at cold temps. Look at the oil's datasheets. Don't need to look at pour point, pumpability - just the viscosity of a 5W synthetic can be less than a 5W dino....it really comes down to an oil formulation question.
A (poor/pour) example would be a cheezy dino that uses all kinds of pour point agents to thin the cold temp viscosity to the LOW side of the 5W range. Sure the oil flows well the first time when cold.....but....
Here's a rhetoretical question: How many dino 0W-X's are out there? There is your answer.
To answer the "why" it's simply the viscosity at cold temps. Look at the oil's datasheets. Don't need to look at pour point, pumpability - just the viscosity of a 5W synthetic can be less than a 5W dino....it really comes down to an oil formulation question.
A (poor/pour) example would be a cheezy dino that uses all kinds of pour point agents to thin the cold temp viscosity to the LOW side of the 5W range. Sure the oil flows well the first time when cold.....but....
Here's a rhetoretical question: How many dino 0W-X's are out there? There is your answer.
"Pour Point" is just a number thrown in to impress the guilable public. How do you define "pour point?"
Eg: A standard 1 litre beaker filled with Brand X chilled to -40 F for 48 hours. Tip the beaker on its side. How quickly must Brand X "pour" out to satisfy a "pour point?" 30 secs? 5 minutes?? So "pour point" isn't even part of the SAE J300 crank/pump test.
For cold cranking we have the standard CCS as defined by ASTM D5293. For most engines, CCS should NOT exceed 3,000-4,000 centiPoise, values that exceed this slow the starter down so much that most diesel engines won't spin fast enough to generate enough heat to fire the fuel.
CCS does NOT determine cold flow, and cold flow is far more important than CCS. An oil may be "thin" enough to allow cranking but be too thick to flow, so no oil pressure.
MRV as defined by ASTM D4684 has an absolute "yield stress" of 60,000 cP. Any MRV value approaching and/or exceeding this could result in no oil pressure or no oil flow in smaller oil galleries.
Most gasoline motors depend on "splash" to get oil on parts of the valvetrain and underneath the piston. Much thicker than 35,000-50,000 cP how can oil "splash?"
An engine sensitive to MRV values benefits from having an MRV value as low as possible, say 10,000-20,000 cP max. Of course there are always tradeoffs: usually an oil with good MRV values will have poor HTHS values, and vice versa.
Given the fact that you will experience MUCH increased wear, even failure, at temps -30 F and especially -40 F, you want first and foremost an oil with a very low MRV.
In pure town driving at temps colder than -30 F, especially approaching -40 F, the motor will never warm up. An oil at or near the MRV BPT will put heavy drag on the motor, so a little intuition should tell us this excess drag will have dramatic effects on fuel economy.
Don't forget the rest of the drivetrain. Automatic transmissions should not have a cold Brookfield viscosity exceeding 100 Poise. Most regular DexIII ATF's are at 100 Poise around -34 F, and most older Type F ATF's hit 100 Poise at -25 F. The torque converter will usually fail to transfer torque at +100 Poise.
By contrast, Mobil 1 ATF has a rated cold Brookfield of 51.5 Poise at -40 F. So we can see there will be MUCH less drag in an automatic at extreme cold temps.
Axles can have a lot of problems at cold Brookfield temps too. Empirical testing has shown that Brookfield's of 1,500 Poise allow "channeling" where the ball bearings in the pinion bearing and the ring gear cut a hole in the oil.
So everything runs dry, usually the pinion bearing fails first as it must support all the rotational torque. Then the R&P goes due to scoring/fretting on the teeth.
Something like Mobil MobilLube SHC 75W-90 has a rated cold Brookfield of 980 Poise at -40 F, with a rated "channel point" of -51 F.
With the cummulative effect of thick motor oil, ATF, and axle fluid, there are dramatic cold temp fuel economy differences.
Even running synthetics in my truck, at -40 F my highway MPG is never higher than 14.5. In straight town driving around 11 MPG. Friends with similar year trucks and motors get 11 MPG highway and 4-6 MPG town driving.
Of course, in sunny funny Phoenix, this is NEVER an issue.
Jerry
Eg: A standard 1 litre beaker filled with Brand X chilled to -40 F for 48 hours. Tip the beaker on its side. How quickly must Brand X "pour" out to satisfy a "pour point?" 30 secs? 5 minutes?? So "pour point" isn't even part of the SAE J300 crank/pump test.
For cold cranking we have the standard CCS as defined by ASTM D5293. For most engines, CCS should NOT exceed 3,000-4,000 centiPoise, values that exceed this slow the starter down so much that most diesel engines won't spin fast enough to generate enough heat to fire the fuel.
CCS does NOT determine cold flow, and cold flow is far more important than CCS. An oil may be "thin" enough to allow cranking but be too thick to flow, so no oil pressure.
MRV as defined by ASTM D4684 has an absolute "yield stress" of 60,000 cP. Any MRV value approaching and/or exceeding this could result in no oil pressure or no oil flow in smaller oil galleries.
Most gasoline motors depend on "splash" to get oil on parts of the valvetrain and underneath the piston. Much thicker than 35,000-50,000 cP how can oil "splash?"
An engine sensitive to MRV values benefits from having an MRV value as low as possible, say 10,000-20,000 cP max. Of course there are always tradeoffs: usually an oil with good MRV values will have poor HTHS values, and vice versa.
Given the fact that you will experience MUCH increased wear, even failure, at temps -30 F and especially -40 F, you want first and foremost an oil with a very low MRV.
In pure town driving at temps colder than -30 F, especially approaching -40 F, the motor will never warm up. An oil at or near the MRV BPT will put heavy drag on the motor, so a little intuition should tell us this excess drag will have dramatic effects on fuel economy.
Don't forget the rest of the drivetrain. Automatic transmissions should not have a cold Brookfield viscosity exceeding 100 Poise. Most regular DexIII ATF's are at 100 Poise around -34 F, and most older Type F ATF's hit 100 Poise at -25 F. The torque converter will usually fail to transfer torque at +100 Poise.
By contrast, Mobil 1 ATF has a rated cold Brookfield of 51.5 Poise at -40 F. So we can see there will be MUCH less drag in an automatic at extreme cold temps.
Axles can have a lot of problems at cold Brookfield temps too. Empirical testing has shown that Brookfield's of 1,500 Poise allow "channeling" where the ball bearings in the pinion bearing and the ring gear cut a hole in the oil.
So everything runs dry, usually the pinion bearing fails first as it must support all the rotational torque. Then the R&P goes due to scoring/fretting on the teeth.
Something like Mobil MobilLube SHC 75W-90 has a rated cold Brookfield of 980 Poise at -40 F, with a rated "channel point" of -51 F.
With the cummulative effect of thick motor oil, ATF, and axle fluid, there are dramatic cold temp fuel economy differences.
Even running synthetics in my truck, at -40 F my highway MPG is never higher than 14.5. In straight town driving around 11 MPG. Friends with similar year trucks and motors get 11 MPG highway and 4-6 MPG town driving.
Of course, in sunny funny Phoenix, this is NEVER an issue.
Jerry
What highway MPG do you get in the hot summer?
It's greek to me.
What do these abbreviations:
CCS
MRV
HTHS
BPT
...mean? Reading your message was like reading Greek. Tell me what all the abbreviations mean, and then I'll go back and try to comprehend.
Thank you.
CCS
MRV
HTHS
BPT
...mean? Reading your message was like reading Greek. Tell me what all the abbreviations mean, and then I'll go back and try to comprehend.
Thank you.
All I know is my oil pressure is 60psi at start up with synthetic. When I used Pennzoil 10W30 at these temps the gauge was pegged at 100 plus psi.
It makes me a lot more secure to see 60 instead of that 100 psi. At least I know the oil is flowing and not just thick oil trying to flow.
It makes me a lot more secure to see 60 instead of that 100 psi. At least I know the oil is flowing and not just thick oil trying to flow.
With the cruise set at 65 MPH, around 20 MPG. On my drive out to Utah last summer, I-80 Nebraska between Lincoln and Grand Island I got 18 MPG with the A/C on and the cruise at 75 MPH. I run Mobil 1 10W-30 in summer.
I'm sorry didn't mean to offend:quote:
Originally posted by batterycar:
It's greek to me.What do these abbreviations:
CCS
MRV
HTHS
BPT
...mean? Reading your message was like reading Greek. Tell me what all the abbreviations mean, and then I'll go back and try to comprehend.
Thank you.
CCS: Cold Cranking Simulator
MRV: Mini Rotary Viscometer
HTHS: High Temperature High Shear
BPT: Borderline Pumping Temperature
Your dino oil was near or at its "yield stress." The oil pump was starting to deadhead and cavitate, I've seen similar readings when there is NO oil flow to the top end.
Much beyond the yield stress of 60,000 cP, and the gauge will remain firmly on the bottom peg.
Jerry
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