Originally Posted by kjohnson
My MC manual requires 89 or higher. Does anyone know if a lower octane (87) gas will have a negative impact on the engine or just have slightly reduced performance?
No reduction in performance. Gasoline is a mixture of chemicals. Octane is included to prevent pre-detonation. (pinging) You know, that rattling noise, some engine will make. If that is happening, it will ruin your pistons.
Simple rule, higher compression ratio, higher octane. Older engines, under 10:1 can typically run 87. If there no engine issues, and gas is of good grade.
I typically run 89, in my Expedition and boat. Both will run will on 87. My MC 205 is a 9.5:1 engine. I usually run 89. I figure 89 is the most sold product, so in theory, could be a more consistant quality.
Also, gas in Oklahoma seems to work better, and usually cheaper, than East Texas. Go figure.