Is mixing octanes allowed?

[wgoodhoofd]

Allow me to explain.<br /><br />New boat, as per my signature. Marina on cottage lake most likely sells only 90 octane (marine grade). While trailering and filling up at local gas station, dad would like to save every penny he can by filling up with 87 octane. Manual says engine runs fine with 87, so is it bad to have part of a tank 87 and part of a tank 90?

 

[thunderroad]

Re: Is mixing octanes allowed?

no...it's fine.

 

[HT32BSX115]

Re: Is mixing octanes allowed?

Correct.<br /><br /><br />From Mercury Marine:<br /><br />2001 models and newer Mercury MerCruiser engines beginning with serial number 0M300000 will operate satisfactorily when using a major brand of unleaded fuel meeting the following specifications:<br /><br /> * USA and Canada – Have a posted pump Octane Rating of 87 (R+M)/2 minimum. Premium gasoline [92 (R+M)/2 Octane] is also acceptable. Do not use leaded gasoline.<br /> * Outside USA and Canada – Have a posted pump Octane Rating of 90 RON minimum. Premium gasoline (98 RON) is also acceptable. If unleaded gasoline is not available, use a major brand of leaded gasoline .<br /><br />Consult the Owner's Manual for more details.<br /><br /><br />Go here: http://www.mercurymarine.com/fueloil_recommendation_faqs#1122 for more info.<br /><br /><br />Regards, <br /><br />Rick

 

[Mile-High Mariner]

Re: Is mixing octanes allowed?

Wgood - have you ever mixed octanes in your car? It doesn't matter a whit to mix premium with regular octane - you just end up with a blend of fuel that contains something between the lower and higher octane number. It's not like mixing different viscosities of oil - that's NOT a good idea - but fuel is fuel, and your new motor will not even notice the difference.

 

[bruceb58]

Re: Is mixing octanes allowed?

Originally posted by Mile High Mariner:<br /> It's not like mixing different viscosities of oil - that's NOT a good idea .

Really? How about Seafoam?

 

[bamadave]

Re: Is mixing octanes allowed?

Rick, where in the U.S can you still buy leaded gas?

 

[whywhyzed]

Re: Is mixing octanes allowed?

Originally posted by wgood:<br /> Allow me to explain.<br /><br />New boat, as per my signature. Marina on cottage lake most likely sells only 90 octane (marine grade).

Not sure about your marina, but most marinas along the trent severn system sell 87 octane. Haven't really seen higher octanes at the dock for 4 or 5 years...

 

[drvred]

Re: Is mixing octanes allowed?

I drive a gas tanker, and the midgrade gas you buy is a 65-35 blend of 87 no lead and 93 super.<br /><br /> Rick

 

[wgoodhoofd]

Re: Is mixing octanes allowed?

thanks everybody, that clears it up.

 

[Mile-High Mariner]

Re: Is mixing octanes allowed?

Bruce - what was your question about SeaFoam? It's a multipurpose additive that goes into solution completely with the oil. I think you may have been thinking of the differences between the flow characteristics of SeaFoam and engine oil but, in the small amounts the manufacturer of SeaFoam recommends that you add the stuff to the crankcase oil, it is of no consequence, viscosity-wise.<br /><br />You can also mix seemingly different oils, such as 5W-40 synthetic with 15W-40 standard (which I faithfully do in my Powerstroke and in my Mercruiser), but they are essentially the same oil. Mixing a multi-viscosity oil with HD30 isn't a good idea, though, because of the disparate viscosity characteristics of each.

 

[bruceb58]

Re: Is mixing octanes allowed?

Mile High,<br /><br />I disagree on the Seafoam. It is basically a solvent, naptha and isopropyl alcohol are the main ingredients. Why anyone would put that in an engine crancase is beyond me.<br /><br />Mixing multi-viscosity and straight grade oil is fine. Multigrade(non-synthetic) oil is also a straight viscosity grade with additives in it to make it act like a different weight.