I would only trust the info in your vehicle's orignal owner's manual compared to whatever woke propaganda the vehicle manufacturer says now about fuel requirements, especially for the older ones. All the 80s owners manuals I remember reading said Gasohol blends over 10% ( IIRC ) are not to be used.
I lost around 2 MPGs when California switched from E6 to E10 15 years ago and 3-4 MPGs 20+ years ago when they switched from MTBE to E6. That was in an 1987 Honda CRX 1.5 DX with an 1985 HF cylinder head, 1985 HF transmission, taller 165-80-13" tires on 1986-7 HF alloy rims, full SMOG delete, headers and some mild tuning. I was getting just under 50 MPGs on the highway with the AC off and 48 MPG with the AC on, at normal 75 MPH freeway speeds. On 55 MPH highways I could get high 60s MPGs with the AC off.
I got back around 2 MPG when I swapped an 1986 HF head with the roller cam and a taller final drive when I built my wagon/HF transmission. I lost around 1 MPG when I added a 1985 SI rear hatch with the duck bill rear spoiler and rear wiper. This was my actual mileage figures that I kept in a log book, updated every fill up by doing the math, not guessing.
The non Si 1st gen CRXs use a CVCC ( compound vortex controlled combustion ) stratified charge lean burn engine, which is basically a Diesel engine that runs on gasoline. The main combustion chamber is fed a very lean mixture that a spark plug can't ignite. A small pre chamber is fed a very rich mixture that when the spark plug fires, the flame shoots out some holes into the main chamber and ignites the lean mixture.
10% Gasohol in my part Florida has been below $3 for a week now.
Welcome Visitor! Please take a few seconds and 
