Synthetic fluids improve MPG?

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Capa

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Ive noticed some people post that a synthetic oil may boost MPG slightly but I've noticed a lot of people post that synthetic fluids will boost MPG. Why? I've also seen several post that synthetic fluids will boost MPG more than synthetic oil. Why?

If the improved MPG is true, I will strongly consider going with synthetic. I would probably change the rear differential and definitely the automatic transmission fluid. What else should I consider changing? I have a Lexus GS400 which I believe calls for Toyota IV transmission fluid. The oil in the vehicle is already synthetic. Is Valvoline Maxlife still highly regarded here, synthetic, and compatible with my vehicle? What about Amsoil's products?
 
Here's my opinion. They do improve mileage. Not a whole heck of a lot though! I think durability and drain interval are the most important aspects of synthetics. As far as fuel economy goes, we are talking about fractions of a MPG.
 
Yes, but its noise. Amsoil ATF and Severe Gear Oil are top shelf products and you cannot go wrong with them. Expensive, but worth it IMHO.

Consider a Magnefine inline filter for the transmission.
 
We are talking about 0.5 to 1.0 percent improvement depending on the transmission architecture and the engine mapping.
 
My long term testing of fuel consumption yielded an improvement of 1.372%, using Mobil 1 engine oil, ATF and differential fluids in a 2005 Subaru Forester. I kept consumption records for ~ 30,000 total miles. The data demonstrated that I could not recover the additional cost of synthetics unless I was willing to exceed the factory recommendations by 4X fluid change intervals, which I chose not to do.
 
They improve MPG only from the fact that they flow better when cold.After they warm up, there is no difference in mpg. There are other reason that you might want to use them other than the minuscule MPG increase.
 
I was talking about transmissions only. If you include RWD then the axle will see about 0.5 percent improvement. You do however have to take into account the other benefits that a true synthetic provides.
 
There is no doubt in my mind car at cold temperatures with ALL synthetic fluids and greases will get better MPG than a car with all conventional lubes. Is the difference humanly detectable using a fill and calculate or a even a standard on board computer? Doubtful.
 
Originally Posted By: Bluestream
They improve MPG only from the fact that they flow better when cold.After they warm up, there is no difference in mpg. There are other reason that you might want to use them other than the minuscule MPG increase.


There is difference even after warm up because of the inherrent characteristics of true synthetic i.e. PAO/Ester.
 
So it seems that many of you are saying that the MPG gain with synthetic fluids are minimum, just like what most say about synthetic oils. If I am to experience any MPG gains, I assume that changing the transmission and differential fluid would suffice?

I am strongly considering Valvoline Maxlife, Redline, and Amsoil as my automatic transmission options. Are all 3 synthetic? Do any of you have any experience with a Toyota transmission that requires Toyota IV and any of these fluids?

Also, would you recommend that I do the fluid exchange before the start of summer or after summer? I had one done two years ago by the dealership.
 
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I have a 98 Toyota Sienna which calls for Dexron III. I've used both Mobil 1 ATF and currently I've switched over to Valvoline Max life which is much cheaper and can be bought in a 5 litre jug.

Both Mobil 1 and Max life are direct replacements for Toyota Type IV. You will not damage your tranny by switching over. There is no ideal time to replace. If you are going to do this yourself, are you doing a drain and fill only, or will you be dropping the tranny pan and cleaning that as well?

I would suggest draining the tranny after the car has been driven for at least 30 minutes.

Regards, JC.
 
On the Lexus GS400, one really cannot drop the pan. It has a mesh screen instead of a filter. These transmissions are known for their longevity. So I will be doing a drain and fill. I believe about 2 quarts are removed and its capacity is 9 quarts.
 
given the basic prerequisites RE: ATF fluid to have proper viscosity and friction properties in order to meet a specific transmission manufacturer's requirements, syn based ATF is designed and blended to be of similar specifications (friction properties, viscosity, etc.) in order to be used in that same transmission.

With these 2 properties in-mind, I don't think you'll gain MPG (if any).

The only benefit of syn ATF (given all else equal) should be higher oxidation resistance (higher temp), therefore, it should lasts a bit longer(inside the trannie).

Q.
 
Originally Posted By: Ken2
The latest version of Mobil 1 ATF is not listed as suitable for transmissions that require T-IV/3309.
http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_Synthetic_ATF.aspx

Capa, while syn lubes will save a bit of fuel, they'll never pay for their added cost. I run syn lubes for their longer life and better protection when very cold and very hot.


Thanks for the info. While my main interest in upgrading was a slight bump in MPG, I'll take extended drains and better heat protection any day of the week. It's gets really hot and cold here so I'm liking syn the more I think about it.

Again, has anyone had a chance to compare Amsoil vs Maxlife vs Redline?
 
The main reason for full synth fluids in trannys and rear ends is for longer life of the components.
They are different than engines in this respect. Lots more shearing is possible.
 
Hi,
Capa -
Originally Posted By: 95busa
Here's my opinion. They do improve mileage. Not a whole heck of a lot though! I think durability and drain interval are the most important aspects of synthetics. As far as fuel economy goes, we are talking about fractions of a MPG.


This has been my experience and there is no "benefit" in using expensive Boutique lubricants either - just the correct specification
 
Thanks Doug for the info. I've narrowed it down to Toyota IV and Maxlife, which are close in price. Maxlife is synthetic, I believe, and slightly cheaper.
 
Originally Posted By: Doug Hillary
Hi,
Capa -
Originally Posted By: 95busa
Here's my opinion. They do improve mileage. Not a whole heck of a lot though! I think durability and drain interval are the most important aspects of synthetics. As far as fuel economy goes, we are talking about fractions of a MPG.


This has been my experience and there is no "benefit" in using expensive Boutique lubricants either - just the correct specification

Will you clarify "Boutique Lubricants". Mobil 1 is a "Boutique Lubricants" ?

Some consider Amsoil, Redline, Royal Purple ... "Boutique Lubricants", but not M1 or Castrol Import ATF ... Some consider Amsoil, Redline ... are high quality fluids therefore the extra cost is justified.
 
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