I have tried different pipes and plugs as well as different venturies( 8,7,5.5) but i can't seem to get more than 8 minutes on a tank. 7 seems to be the best venturi though...it gives 30sec more.
I run 1/8th buggy and a Sirio STi engine.

I'm about to try 16% nitro instead of 25% i run now.
Has anyone tried this and has any input on the results?
Power wise i don't think i'll have any problems since it's already overpowered so if someone has tried it i would much appreciate the info.

8 minutes is a fairly good runtime for a tank (you do not state which track, which car, pipe/manifold combo and what are your traction conditions).

The key for more runtime sometimes is your throttle finger. Being gentler on the throttle makes much difference.

Maybe you can try with a lesser powerful engine. Sometimes, power is not everything...

Edit: Readed you signature: Have you tried with a Sirio pipe?. That nasty habit of Mix & Match engines and pipes from different manufacturers ruins all the work from the engine maker.

Yes i tried the 2013.Which gave the best runtime.

I just want to know about the lower nitro content...if and how much will it affect runtime.

It's hard to say exactly how much run time you would get but going to 16% will definitely improve it.

How noticable is it on .21 engines.
Can it be compared to smaller venturies or much less?

G'day mate, I know the Australian 1/8 buggy champ runs only 3/4 throttle so dial back that EPA. He gets about 11mins per tank i think i remeber hearing. I could be wrong but seems as though the motors are hugely overpowered anyway it doesn't matter and makes it a bit more useable.

i know a lot of guys here in florida are racing 16% nitro in onroad cars and you cant tell a different in power i have been using it for 3 races and am loving it.

the sirio buggy engines are known for not the best mpg...Look at Lutz' statement when he left kyosho 'engine with more runtime'.....