Change ATF -worse mpg?

[RugbyPete]

Has anyone noticed any difference in MPG since changing their ATF to amsoil stuff?

I'm either revving around a lot more due to the smooth gearbox or I'm getting lower mpg from the effects this slippery stuff is having on my box... I can't decide... anyone else noticed anything?

I'm thinking efficiency could be lost to the torque converter's internal slippage, if so we have a compramise for the superior protection.

[I-S]

My mpg improved slightly and the box runs cooler and fewer revs for a given road speed.

[RugbyPete]

So your saying your torque converter was biting MORE with the amsoil?

I can't say anything about temperature, I have no way of monitoring the AF temp.

[I-S]

Yes, the torque converter bites more with the Amsoil than with the knackered (ie light brown) fluid that was in there before.

As for temperature monitoring, I have no direct way of measuring it, but the engine coolant temperature is now lower. The ATF cooler is built into the radiator and the ATF is higher temperature than the coolant, so the drop in ATF temp has a knock-on effect on the engine temp. It was a noticeable drop in the coolant temp that coincided exactly with changing the ATF.

[RugbyPete]

Ok, but, correct me if I'm wrong but doesnt the torque converter rely on friction to transfer torque from the engine through the gearbox?

If so, you need some friction to get things moving, if you're is biting more with amsoil surely its creating more friction.
I feel I'm getting too much friction reduction, causing less power to transfer through the torque converter and hence the bad mpg. A bit like putting dexron 3 in and using too much friction modifier.

My temp has reduced too. Again, some torque converters dont work well if things aren't lovely and warm, but again I don't know the AT boxes thresholds

[Wodjno]

Has anyone noticed any difference in MPG since changing their ATF to amsoil stuff?

I'm either revving around a lot more due to the smooth gearbox or I'm getting lower mpg from the effects this slippery stuff is having on my box... I can't decide... anyone else noticed anything?

I'm thinking efficiency could be lost to the torque converter's internal slippage, if so we have a compramise for the superior protection.

Didn't i see you post in another thread, that the Nitrox Stuff had given your engine a new lease of life ??
There for i presume from this, that you have more power, and therefore are using the power for the :evilgrin: factor :inquisiti

Is it not this :speechles That is having an affect on your fuel consumption ?? :thinking:

[Kieran]

Didn't i see you post in another thread, that the Nitrox Stuff had given your engine a new lease of life ??
There for i presume from this, that you have more power, and therefore are using the power for the :evilgrin: factor :inquisiti

Is it not this :speechles That is having an affect on your fuel consumption ?? :thinking:

I was just about to say what Glenn's just said!

[I-S]

The gearbox relies upon having the right amount of friction and the right amount of slip within a certain range. Amsoil ATF falls in that range, Dexron 3 does not, SP III does. D3 with friction modifiers can also fall into that range. With too much friction modifier it will also fall outside of that range.

Amsoil is no smoother than a brand new box full of SPIII. The point is that with these cars reputation for chewing ATF the fully synthetic Amsoil's resistance to breaking down at higher temperatures means that the fluid will last several times longer and is actually cheaper in the long run. My Amsoil ATF is now 15000 miles old and still looks the same red that it did when it came out of the bottle.

It does sound like you're putting your foot down a bit more which may mean that the box is using the torque converter more than it would otherwise. That combined with using that power (more power = more fuel) will have far more impact on mpg than any differences between ATFs ever will.