Synthetic and Fuel Economy?

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I sorry if I'm I did a search, I swear, and found nothing, recent at least. I know it's almost impossible to gauge for the average person, seeing as so many factors come into play regarding avg. gas mileage on any given vehicle. Factors such as ambient temperature, road grades, not filling the tank to the top throwing off calculation, weather conditions, wind, avg. speeds and acceleration styles, etc. But do most here believe that you get perhaps an ever-so-slight boost in fuel economy using synthetic oil of any of the three groupings, especially Groups IV & V? For me, the anecdotal evidence says "yes." My experience is that I've had some minor to some not-so-minor gains in mileage after switching from conventional oils to synthetic while driving long distance. Day-to-day local driving, not so much... But --I know I've read a study done by some university in which they tested the fuel usage by comparing two identical tractor engines; one running Mobil1, the other running Havoline, with both weights at 10W-30. The result was that it was a wash I believe. But then again, I'm not sure this adequately replicated everyday driving...
 
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But do most here believe that you get perhaps an ever-so-slight boost in fuel economy using synthetic oil of any of the three groupings, especially Groups IV & V? For me, the anecdotal evidence says "yes." My experience is that I've had some minor to some not-so-minor gains in mileage after switching from conventional oils to synthetic while driving long distance.
FWIW: That's my experience as well. As far as I can tell, I get a little better gas mileage and a little better power on synthetic oil (not to mention a longer OCI, and a cleaner engine).
 
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Nick, Synthetic vs conventional with both oils having the same viscosity in the tested temperature range will be a tie.
 
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If your objective is to maximize fuel mileage, then you really only have to do two things to consider. 1. Buy an oil that is API SM rated and has a Starburst symbol on the label. You then know it has actually been tested to a standard that requires it to save fuel, and 2. Choose an oil with the lowest possible viscosity that meets your car mfg's recommendations. Many are now recommending 5w20. If that does not narrow the choices to an acceptable number then compare the specs for the oils left and choose the one that has the lowest HT/HS viscosity number. Testing has shown lower HT/HS means better fuel economy and more HP. A 5w20 should be at or near 2.6, and a 5w30 should be at or near 2.9.
 
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Castrol SLX delivers like 2%-3% mpg gain verses 15w-40, with the same 3.5cP HT/HS, as per Audi and Castrol research.
 
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Auto-Union, Of course, we should remember that SLX is a 0W30 product, and the test you're referring to included a operating the vehicle beginning at a fairly cold temp.
 

Bill in Utah

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As someone who keeps track of every tank vs miles driven I've never had better mpg using Syn over conventional in all types of engines (v6,I4,V8,I6). Grade of oil (5w-30 vs 10-40) makes more of a differance.. The biggest differance is (other than type of outfit your driving) your right foot ... followed by tire pressures! Take care, Bill
 
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Well, here is a post of my mileage gains after switching from 5W30 synthetic to 0W30 synthetic. I am going to update the thread with a new MPG post, but it keeps increasing even though the ambient temp is starting to get a little cooler. However, I think most of my gains come from the fact that I only drive 5 miles at a time and the oil never gets up to temp. The 0W helps in MPG by letting the oil pump out of relief faster (if not completely). Amsoil 0W30
 
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My wife and I have two 03 vehicles which I switched to synthetic, using the same viscosity as the previous dino. I've checked both vehicles numerous times and the syn gives no better mpg than the dino.
 

ALS

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Not much difference in an engine. The biggest increase you will see if the conventional oils in the transmission and differential are replaced with synthetic. 25 years ago there was a pretty big difference between synthetic and conventional oils. With the new additives and refining technology there is almost a zero increase in gas mileage between conventional and synthetic motor oils with the same viscosity.
 
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Viscosity is your main economy killer during warm up. Synths have a head start in thinning out. No brainer if you're a short tripper type. You should be able to measure the difference. The long commuters won't be able to track much difference except long term (remember, of the same visc)...so they're also going to be subject to so many other "detuning" variables (tune, tire pressure, etc...etc.) that it makes it nearly impossible to determine accurately. You just have to juggle too many variables. You would have to be a fleet operator that already accounted for all the stuff that trashes economy and have a program in place to cope with them ..then you may see a difference in how many gallons per month you're buying. I doubt too many of us can look at it that way.
 
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Good points Gary - as I tend to drive only when and as far as I need to, this has been appearent in the colder winter months.
 
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I've seen economy improve 6% going from a dino 15W-40 to a GF-3 0W-40 synthetic (M-1). Also seen it drop 6% (from the 0W-40 M1)when going to a competitor's 0W-40 synthetic with nearly 2cst lower viscosity. Picked up most of that gap going to a 5W-40 GrIII and ester oil, back up in the high 14s viscosity wise. Made me realise that thinner oil does not necessarily mean better economy. Synths don't necessarily mean it either. A bit of experimentation, and you can save the cost of the synth in fuel savings during an interval...may take a few changes to get the trend, 'though.
 
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I run synthetic in all my cars, and I've never noticed a difference in MPG when switching. I think the biggest factors in MPG are non-oil related, like weather, tire pressure and how hard you hit the ol' gas pedal...
 
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The main advantage to synlubes in terms of fuel efficiency is that you can substitute a lower viscosity product without compromising on wear protection, oil consumption etc. For example, you can run a very high quality 0w-30 synthetic (GC/0w-30, Amsoil Series 2000), in place of 10w-30/0w-40/5w-40 oils and you can run a 5w-30/10w-30, CI-4+ rated synthetic HDEO in place of 15w-40 grades. I have seen small but consistent gains in fuel efficiency of 2%-4% by making these substitutions, while maintaining excellent wear control. Changing over the transmission and differential(s) to low viscosity synlubes will typically provide an additional 1%-2% fuel savings. Changing the power steering fluid over to a synthetic ATF reduces the parasitic losses during low temp operation as well. My advice is to change to synlubes bumper to bumper if you're looking for improvements in performance and fuel efficiency. TS
 
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Hard to tell since ive been using synthetic since pretty much day one...although my engines internals sure look pretty.
 
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