None that I could see in two vehicles, and certainly not enough for me to care or want to change back to a 20 grade.
How much fuel economy difference 5-20 vs 5-30?
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The improvement in fuel economy that you might see is implicit in the ILSAC specifications.
Take the Sequence VIB test for example (yes I know this has been superceded now but it's illustrative)...
Relative to a FIXED reference oil (an SAE 30?) you need to meet or exceed the following fuel economy improvements after 16 hours engine operation...
10W30 1.1% FEI
0W30 & 5W30 1.8% FEI
0w20 & 5W20 2.3% FEI
FEI is remeasured after 96 hours operation to confirm fuel economy durability. All of the above spec numbers drop by 0.3%.
So, all things being equal, you might, on average, expect a 0.5% worsening in fuel economy in moving from a 5W20 to a 5W30.
To all the folks that say, 'there's zero difference', 'it gets lost in the noise', 'it will get masked by differences in fuel density and tyre pressure', you're all 100% correct but at the same time, completely wrong. That oil viscosity impacts on fuel economy is scientific fact, not fiction (Ye canny change the laws of physics Captain!). If say the entire US vehicle parc was to move overnight from 5W20 to 5W30 (like the OP suggests) then over time, all things being equal, you WOULD see a small increase in sales of gasoline at the pumps. Within the parc however, some would see nothing, some would see a worsening and a lucky few would undoubtedly see FE improve!
It's this 'mass effect' that is behind the global move to ever thinner oils; not what any individual punter sees on his or her motor.
Take the Sequence VIB test for example (yes I know this has been superceded now but it's illustrative)...
Relative to a FIXED reference oil (an SAE 30?) you need to meet or exceed the following fuel economy improvements after 16 hours engine operation...
10W30 1.1% FEI
0W30 & 5W30 1.8% FEI
0w20 & 5W20 2.3% FEI
FEI is remeasured after 96 hours operation to confirm fuel economy durability. All of the above spec numbers drop by 0.3%.
So, all things being equal, you might, on average, expect a 0.5% worsening in fuel economy in moving from a 5W20 to a 5W30.
To all the folks that say, 'there's zero difference', 'it gets lost in the noise', 'it will get masked by differences in fuel density and tyre pressure', you're all 100% correct but at the same time, completely wrong. That oil viscosity impacts on fuel economy is scientific fact, not fiction (Ye canny change the laws of physics Captain!). If say the entire US vehicle parc was to move overnight from 5W20 to 5W30 (like the OP suggests) then over time, all things being equal, you WOULD see a small increase in sales of gasoline at the pumps. Within the parc however, some would see nothing, some would see a worsening and a lucky few would undoubtedly see FE improve!
It's this 'mass effect' that is behind the global move to ever thinner oils; not what any individual punter sees on his or her motor.
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Originally Posted By: Broo
I agree with CaspianM, I doubt the fuel efficiency loss would be measurable. If your manual specifies to use 5w20, use that. If you're worried about the engine aging, switch to a 5w20 high mileage oil.
I agree too. I've tried it in my Grand Marquis. No measurable difference in MPG, no real difference in performance. I figure if 5W-20 got it to 140K+ miles in the southern Ca. and Arizona desert heat, why mess with it?
Could it be those Ford engineers knew what they were doing when they recommended 5W-20? They knew that "thin watery oil" would protect the engine when climbing a long hill at 75-80 MPH on a 115F degree day? Amazing!
I agree with CaspianM, I doubt the fuel efficiency loss would be measurable. If your manual specifies to use 5w20, use that. If you're worried about the engine aging, switch to a 5w20 high mileage oil.
I agree too. I've tried it in my Grand Marquis. No measurable difference in MPG, no real difference in performance. I figure if 5W-20 got it to 140K+ miles in the southern Ca. and Arizona desert heat, why mess with it?
Could it be those Ford engineers knew what they were doing when they recommended 5W-20? They knew that "thin watery oil" would protect the engine when climbing a long hill at 75-80 MPH on a 115F degree day? Amazing!
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