There are some Gas Stations that tend to be RV (And Semi truck) Friendly which have web sites.
Flying-J (now owned by Pilot)
TA (Travel America)
To mane a few.. In addition there are other very good truck stops I will name 3
Arlene's on the west side of Battle Creek, MI (First Battle Creek exit on East bound (94, I think the named road is Sklyline Drive but it's been a few years)
Tekon Truck stop (M-60 just east of I-69 in Tekonsha,, I mean Just east
TeKi (I-94 and 11 mile road, in the "Mar-Creek" area (Eastern most Battle Creek exit) Mar-Creek is short for Marshall-Battle creek it is half way between.
The three main ways into Michigan are I-94, I-69 and I-75
On I-75 and West Road, well south of Detroit, is "The Detroiter" truck stop On the east side of the freeway (As in borders the service drive if there is one there)
IN addition many regular gas stations can take an RV.. I can give you a short list of RV friendly stations (Meaning easy in and easy out) in S.E. Michigan including the Shell at 7 mile and Grand River in Detroit.. If you are going n/w on Grand River and your gas cap is on the RIGHT (Passenger side) you turn into the station, take the outer most pump and then pull straight out onto 7 mile, NO turns on station property. If your gas cap is on the driver's side.. Go west on 7 mile toward Grand River and.. Well. you must turn right (n/w) on to Grand river but there are plenty of lanes.
IN Davison Michigan, Irish Road and Cort street (just north of I-69) Speedway has a lot of clearance,, Pump one... If gas cap on right enter off COURT, on left enter off Irish road. Two turns (right and left) on station proprty but lots of room.
NOTE: the two specific stations I mentioned tend to have lower prices than many surrounding stations.
At the 7-mile/Grand River station there is a nearby Marathon (7 and Telegraph) always crowded, Major issues getting in and out, and never cheaper. Why they get so much business and the Shell does not.. I do not know. There is also a B-P at 7 and Tel, hardly ever crouded, 5 cents per gallon more (usually) than the other two.