When my boat engines where built in 2003 they were designed for 89 oct. MTBE blend fuel and dynoed at 647 hp. A few years later, due to a vacuum leak on the intake manifold, I melted a piston at the same time E10 was being introduced. In the interest of saving money after a rebuild, I suggested tuning the new engine for 87 octane. After a few hours on a dyno and many trial and error "pulls", we wound up with 661 hp on 87 oct E10
. We then matched the tune on the other engine and saved about 10 cents a gal. even though it uses a little more of what we are being "forced" to use.
