Manual says 87 recommended, but specifically for the ecoboost version, which I have, it adds that 89 "might improve performance."
I've defaulted to 87. However an issue has arisen with the car not starting--it cranks forever, but never starts. This is intermitant. Once it finally does start it starts reliably until we leave the car off for more than 12 hours or so.
A mechanic, based on a code he got, says he thinks the issue is I've been using the wrong grade of fuel and it has messedd with my evaporator or my "turbo". (I admit I don't really know what that means in this context. He pointed to a part of the engine towards the front with three slots in it.)
On this model with this engine, do you use higher grade gas? Does it sound plausible that switching will be necessary to keep this engine-start problem from occurring?