Are Synthetics really more fuel efficient?

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Oct 26, 2003
Granville, Ohio
I've read several posts where people state that "synthetics" (implying all synthetics) get better gas mileage than comparable weight dino oils. Can anyone tell me where the source of this information comes from? I'm not saying that it's wrong, I just can't rationalize it in my head. My experience years ago when I switched between the two seemed to be the opposite. I read a post in the last few days of someone else that had similar comments. I'd be more inclined to believe it has to do with the level of friction modifiers in the oil, and that many synthetics have more than the dino oils. That implies that there is nothing inherent in G-III or G-IV oils that gives them a lower coefficient of friction (it wouldn't surprise me if G-V oils are different). I'm not looking for testimonials. I know there are lots of people that feel they're getting better fuel economy. I also know that there can be a placebo affect. That's why I'd like to see the facts.
Is Ice really "slippier" than water? Be it Mobil 1, Redline, Amsoil, Royal Purple, German Castrol Syntec etc...these will lower engine friction. You may not see a sigificant driveline MPG+ increase unless you go all me *lol* and run your engine, trans, differential and all with synthetics. Synthetic = PAO or Ester to me just to clarify.
Not all oils are created equal. Each oil must stand on its own regardless of the CLASS or TYPE it falls within. Some dinos outperform most Syns here or at least come within the same playing arena to give a real duel. Now, that being said, MPG is not everything. Not alone IMO, only a factor. One needs to look at the UOA's too. Then I would say if the UOA's support the MPG, then run with it.
To be honest, I do not understad how anybody can say they've seen increase in the gas mileage. I've been meticulously recording the gas mileage for one of my cars for about a year -- and it varies from 31mpg to 37! Granted, 37 happened only once, in mild weather, no AC or heat used, etc., but mpg always fluctuates from 31+ to 34+, depending on the driving I do. Is there a trick I do not know of?..
In motor oil, if the viscosities are exactly the same there will be no detectable MPG change. However, recent posts will atest, some pretty nippy days and nights have been here. Intuition and research tells me synthetics flow better at cold...and strictly vs. a dino oil, one should get better mpg with synthetic during the oil warm up phase. To be honest the only cars I have seen change MPG for the better are AT's, when the motor oil, AT and diff. were all switched. 2mpg or so. Ma-phia - don't worry you are normal. This is my experience too. Varies with turdbo usage.
It would be hard to say if syns. are better especially with the hydroisomerized oils. The heavy duty hydroisomerized oil would give any premium syn. oil a run for its money .But the premimum syn. oils have way better freezing weather performance ,ultimate high temp protection won't breakdown on itself like group I oils so they are cleaner and diesthers and polyolesters are cleaners themselves. Some tout more film strength?. Petro oil works just fine if changed on a regular basis ,most of the time it is not. IMO the worst thing that can happen using syn. oil is at worst you spend extra money up front . I have used syn.oils for years in all my vehicles and never noticed any m.p.g. improvement using it from front bumper to rear bumper. In my wifes super duty i will be using a ci4 petro oil cause from my experience at work Delo 400 is great oil and all the other h.d. oils are at least comparable. Might even not go back to my syn. for life Toyota pickup.
Thanks for the posts, guys. It has confirmed what I've believed all along. Pablo's comments are the same as my thoughts. I saw a post on another site from a guy that said that the cost difference between the two is more than offset by the increased fuel economy of synthetics. There's another post floating around this forum making the same claims.
Pablo, I don't have a turbo on my car. It's a completely stock (with exception of custom wheels) 02 Ford Focus ZX3... I guess, you meant that you have it (turbo). I am sure gas quality also contributes to differences in mpg, I try to refuel at a decent place usually, but it's not always the same one. I used to be able to tell if gas was of good or bad quality by its smell, but I kinda forgot it now. I changed over to 0w20 M1 last Sunday, and my first observation is that the engine runs a notch cooler. Less friction, I guess. [ January 23, 2004, 06:53 AM: Message edited by: Ma-fia ]
My '97 Town car gets about 2 mpg more mileage than my previous '92==same road, weather conditions, and speed in several 142 mile trips. Both used M1, 5-30, but the ninety seven also has M1 trans fluid, and Penz synthetic differential fluid. I am convinced that there is a 2-3% increase in mileage with these cars,when all fluids are synthetic. [ January 23, 2004, 07:12 AM: Message edited by: blakegeo ]
Yes they are. The main reason I use them is because of protection. I live 200 yards away from the highway. I start my honda and drive right onto the highway and am doing 60-70 right after start up. I dont sit there and warm it up. Protection and ease of flowing in the eninge thats why I love them.
Originally posted by Pablo: However, recent posts will atest, some pretty nippy days and nights have been here. Intuition and research tells me synthetics flow better at cold...and strictly vs. a dino oil, one should get better mpg with synthetic during the oil warm up phase.
Really? Why?
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