Octane recommendation in 5.0 mph mercruiser

[woodguy81]

I have been running 89 from the pump with ethanol bc I can find gas without it. I use Star tron additive to help with this. Is there any reason I couldn’t run 87 and get a little more? What’s everyone’s opinion on this?

 

[GA_Boater]

Gasoline octane isn't going to help if you have 5.0 MPH Mercruiser.

Sorry, but can you reword your question because none of it makes any sense?

 

[tpenfield]

I agree 5.0 miles per hour is pretty slow.

FWIW - I don't think the engine will care if you feed it 87 or 89 octane.

 

[garbageguy]

Assuming you mean 5.0 liter, my .02 is to run 87, I don't think 89 will help you

 

[thumpar]

I run 87 in mine.

 

[QBhoy]

Hi
presumably you mean a 5.0 mpi. I have ran 99 in line loads of times and haven’t noticed a real difference to be honest. If anything I think it’s confuses the MPI ecu and it’s adjustment of timing etc. Waste of money really. These thing are simple beasts.

 

[woodguy81]

Yeah. 5.0 mpi. Autocorrect got me there

 

[Bondo]

Ayuh,..... I always ran just plain ole "Regular" gas in mine, til the ethanol free gas became available,.....

The ethanol free gas is Hi-test,.....
It don't make any more power, but will help with spark-knock, aka; detonation, but that's the only benefit,...
'n it's ethanol free of course,......