87 vs 89 vs 93 octane - my findings

[Jeremygsu]

I have a long commute for my job (75 miles each way) and purchased a '15 Expedition XLT back in March with 49k on the clock. I sold my '16 Tundra 4x4 and was curious on what the Expedition would get with the various octanes as I had heard the turbo'd engine was more affected by the octane ratings than a normal gas engine.

I decided to keep a log and run 5 tanks of each octane to see if there was a difference. The daily route is from Ocala, FL to Orlando and back. I tried to keep the speeds consistent using cruise control as much as possible and minimizing idle time. I typically ran 72mph down and 80mph back. I also reset the computer at each fill up and compared that to hand calculations.

Here were my findings:

87 octane -
Calculated vs computer
17.20 vs 18.1
17.10 vs 18.1
17.30 vs 18.5
16.20 vs 17.3
17.50 vs 18.9

87 Avg 17.06 vs 18.2

89 octane
17.10 vs 18.3
16.89 vs 18.2
17.77 vs 18.7
17.45 vs 18.7
16.85 vs 18.1

89 Avg 17.21 vs 18.4

93 octane
18.56 vs 19.8
18.36 vs 19.6
19.58 vs 20.8
18.00 vs 19.0
17.34 vs 18.2

93 Avg 18.36 I forgot to record the computer recording for the last fill-up.

So 93 octane does yield better mileage but will cost you more money.

It also showed that the computer is not accurate compared to Fuelly or hand calculations.

I am going to try 5 tanks of 91 next to see what that yields.

This was just for my personal findings and nothing else.

Jeremy

 

[210M]

This is good stuff... Thanks for putting in the time and effort. Did you notice any significant difference in engine performance?

 

[Boostedbus]

Is your Expedition 4x4 and regular wheel base? Also what axle ratio do you have? I also assume you are running air conditioning and not windows down in FL.

 

[Jeremygsu]

This is good stuff... Thanks for putting in the time and effort. Did you notice any significant difference in engine performance?

Honestly, I didn't get on it that much during these trials to really get a good feel of the power difference. I think it had more umph and ran smoother, but to be honest before I started this I didn't think the power was bad running 87. Coming from my 5.7 Tundra I thought the mid-range power was great once you got past the turbo lag.

 

[Jeremygsu]

Is your Expedition 4x4 and regular wheel base? Also what axle ratio do you have? I also assume you are running air conditioning and not windows down in FL.

Sorry. Mine is a regular wheelbase 4x2 and I am unsure of the rear axle ratio. My commute is about 69 miles highway and 6 miles side road. Yes, I ran the A/C the whole time, sometimes blasting it the whole way.

Another note, I was actually able to keep my cruise control on more during the initial 87 testing because of Covid there was nobody on the freeway. During the 93 tests I had to take it off more frequently because of traffic. The tests may have yielded even better results if I could have done it in April as well when we were shutdown.

 

[mquick5]

My 2017 xl 4x4 averages 13.7 but on the freeway sometimes the dash thingy will show well above 20mpg on 87 octane.

Sent from my SM-G930T using Tapatalk

 

[JasonH]

This is good stuff... Thanks for putting in the time and effort. Did you notice any significant difference in engine performance?

There is a readily discernible difference between 87 and 93 octane. I tow on 93 only, but even without a heavy load I can feel the difference. The engine pulls timing on 87 because the difference is noticeable even at part throttle, where peak boost wouldn't come into play.

 

[07navi]

So what's the bottom line? More power? Better mpgs? Worth the extra money? Only good for towing? Good for all years? Waste of money?

 

[Aspen03]

So what's the bottom line? More power? Better mpgs? Worth the extra money? Only good for towing? Good for all years? Waste of money?

Based on the data just cruising down the hwy on 93 looks to be a loss, financially speaking. A 10% mpg gain w a fuel that's 20% more costly in most areas. Around here it can approach 30% with gas prices where they currently are. Of course the data isnt really useful for all years. The 15 is a completely different everything from likely 70% of the expeditions on the road today.


OP: I've seen similar results in my 2003. I run through a tank every 8 or 9 days and while on a commute what so else do I have to do other than track mileage. 93 routinely nets me about a 1-1.5mpg increase...why I dont know because I'm cruising at 67-68 and rarely if ever sit in traffic and engine load is low. Just stop light here and there. On a 5.4 that's about a 10% difference as well. Gas from same station, same pump and I generally run it down to about 40mi range beforehand which results in about a 26g fill. If I'm loaded up w the whole gang and packed full 93 does tend to run better in my experience.

I'm kind if shocked you dont get better being a 4x2. I'm in a 4x4 EB with 221k on it and average out just shy of 16 most of the time. Of my 24mi commute each way there is 17mi hwy so I actually have more in town than you do from a percentage of the drive than you but I would say the difference in traffic is probably what gets you. My last tank I averaged 14.86 but I was also relegated to drive through for lunch and ate in the car a couple times w AC going. That was easily an hour of idle time amongst the days.

 

[Boostedbus]

I'm kind if shocked you dont get better being a 4x2.

He said he’s running 80 mph on the trip home. I know my mileage suffers when I crank up to 80 - 85 mph. I’ve got 3.73 gears though. Lower gear ratios come into play more at high speeds especially on flat ground in Florida. He probably doesn’t have 3.73’s with the 2wd and doesn’t need them on flat ground unless he’s towing a parachute. I’m sure he could do better if he wanted to , but I think his goal was to be consistent in all tests with his driving style. There is no way I could be that consistent even with one tank. I’d be too impatient and have to WOT around someone if they were just creeping along.