Hi, We have had our new '18 Envision Premium since May 25th. So far we have 3,025 miles clocked including one vacation trip. I have been using premium and mid grade fuel either Shell, Exxon or Mobil. I know some say you can and some say you can't use regular fuel but was wondering if anyone has been running theirs on it and if so how is the performance? Is it substantially reduced or have you developed pre ignition knocking? Any insight will be helpful. Thanks, Mark

The 87 octane will have a slight, noticeable power drop over 92-93 octane. A slight drop in fuel economy and some audible pinging with the windows down.

I've run all grades and currently mixing E85 with 87 octane.

Just a little update. Well, the car is up to a little over 10K miles now and I have tried numerous types (regular, mid and high-grade versions) and brands of gasoline (all name brands, I checked the GM site for authorized brands). I really feel the performance is best with the high octane fuel even though I am not a hard driver. The car is smoother, has more pep and I hear no engine noise (pinging or otherwise). The upside is I generally get about 25-28 all around driving mileage. The downside is the premium that I have been buying is between $1 to $1.20 more than regular a gallon. Shell today $3.549 @10.397 gallons nets $36.90 which included a $.05 savings per gallon with the Shell card. Still, I am spending less than I did when I had the 3.6L V6 and the performance is almost as good with far better mileage so I fill up far less often.

I found the octane matters little for mpg. The 2.0T does have more pep with higher octane.

I've been mixing E85 and 87 octane. I mix 30% E85 and 70% 87 octane for about 93-94 octane. Cold start is good so far at 25°F degrees but mileage does suffer with E85.

Comparing AWD cars, I own a 2013 Subaru Legacy that runs on regular (H6) and a 2018 Envision on Premium. The cars have the same acceleration. I average (same mix of driving on both cars) about 21 mpg in the Subaru, and just over 25 mpg in the Envision. So each week filling them up, I current spend about $28 on the Buick, and $30 on the Subaru. So while I use premium, I actually spend less in the same driving than the Subaru. We could not get the 4 cylinder subaru because the car did not have enough acceleration for the Merritt Parkway and some of its 50 yard on ramps to get to 55 mph. So a regular car with the same performance getting worse gas mileage costs me more.

How is the acceleration of the turbo-4 vs thr H6? Not sure if there is elevation involved.

The 2013 Subaru Legacy 3.6R and the 2018 Envision Premium II I own (2.0L turbo) have about the same acceleration. The Subaru is rated at 7.0 seconds in most tests, the Envision is about 6.5 to 7.0 seconds depending who tests it, or very close. Both are more than adequate for merging on short ramps on to highways. The elevation is about 250 feet above sea level where the highway is located. I don't do hard acceleration on top of the mountain where I live, about 650 feet above sea level (base of mountain about 100 feet above sea level). Hope that helps.

Note that in 2020 Subaru will no longer sell the H6, just the H4 and the H4 turbo themselves running on premium. It is the way the industry is going (the new turbo from Subaru will generate the same power as the discontinued H6, but will weigh less so accelerate faster most likely).