Honda Genny Gas

[Matt Irwin]

I've noticed a number of rental houses requiring the use of 91 octane gas with their Honda gennys (I often use the EU3000is), but the Honda user manual specs' 87 octane as the fuel to use.

 

Does 91 prolong the life of the genny and/or improve performance? Fewer oil changes? Is there any downside to using 91 (aside from price) with the Hondas?

[Walter Graff]

Just like in a car, whatever the manufacture recommends is what you should use. That octane rating is based on mathematical formulas for known compression ratios for the engine. You say Honda says 87 octane. Anything more does NOTHING more for the engines life, performance or anything else. In fact they are probably hurting the engine even more. The higher the octane the more pressure needed to ignite the fuel. They are damaging the spark plug sooner, and the engine like this that is designed with a lower compression ratio actually performs worse with higher compression rated gas such as 91. Here is the myth: Higher octane fuel is NOT better quality fuel. It simply means that it takes more compression to ignite the fuel. The more pressure the more wear and tear on an engine with a known compression ratio that is below what higher octane fuel gives. And you also get the side effect of more unburned components in the exhaust and additional wear and tear on the exhaust system, plus more pollution. Those Honda engines are small with small bore pistons so using higher octane is making the engines work harder and in fact shortening the life of the engine, not making it more efficient as myth would have most folks believe. It's a common myth that higher means better just as it does with high def numbers and like high def, it's often a falsehood. Sounds like these guys fell for it. Give them my post and tell them to call me and I'll explain the science of how octane works and why they are hurting themselves and their equipment.

[Matt Irwin]

Makes sense to me. Thank you Walter.