With gas prices on the rise, reg unleaded where i live just hit the 4$ mark and E85 is sitting at 2.99$
is that a good enough price difference to make the switch while prices are high ??
or is the mileage loss great enough to just keep running my 90 octane??

 

Yes switch more than enough just make sure to run a tank of regular every third tank or so

 

How much mpg will you lose? There a station selling E85 near me but never tried it.

 

if you are running 90 in a 5.4L you are wasting your money and gaining nothing, 87 or 85 octane is all you need. however at 1$ cheaper i would switch to e85 for sure.

 

Not sure exactly the mpg you lose but figured it out when I had my 2010 at .47 cent difference you were braking even so you will be far ahead at a dollar difference..just remember the manual tells you to run a tank of regular every third our fourth tank. You would need to check to be sure.

 

Also change your oil more often, use what schedule your manual says for e85.

 

Might be a dumb question, but what if you run full synthetic oil? Do you still have to change it at 5K with e85 or could you keep an eye on it and possibly go 7500?

 

Well Im no expert, in fact I havent even read the manual, but if it were me I would change it the first time at 5000 or whatever the manual suggests and take a sample and have it analyzed, if it comes back good go longer next time and send another sample, however oils cheap compared to a new engine and I usually change mine around 5000 miles anyway, I run synthetic blend.