I'm done with low octane fuel

[GenesisGuy70]

The Accord in my sig says "87 or higher" in the manual. Due to the small engine, high compression, turbo and direct injection, I always run 93. Might not be making a difference at all, but I feel better using it. Can't possibly see how the same gas I used in my '99 Grand Am is just as suitable for this much more advanced engine. With the fuel dilution problems the 1.5T has experienced as well, I feel better running 93.

 

[Kestas]

I too went the other way and use 87 octane. I gave up some top end acceleration to save 28% on my gasoline bill. I can still go 70-80 mph on the freeway with no loss in gas mileage.

 

[y_p_w]

Well - maybe a few thoughts.

Depends on the vehicle. I know for sure that 91 (R+M)/2 will help improve performance of several cars I've owned or driven, including my parents' 2001 Camry LE V6. Kind of goes against what most would think about a sedate family grocery getter, but it said 87 required and higher octane would improve performance. A lot of flex-fuel cars will do better with anything higher octane rated. Obvious the best performance with E85, but then that means lower energy content. But still more efficient given the energy content of the fuel.

Also - it's weird around here. 91 is and has been the standard premium for nearly 20 years in California. 92 used to be the standard and only independents would have 91 on the pump, although I suspect it was for flexibility since that's only the minimum requirement. I saw 92 available on a trip to Washington state. Around here any place that we can fine 93/94 octane it's blended with 100 octane street-legal race fuel. Here's one of the pumps at a local place that has 100 octane and assorted fuels that are blended with the 91 and 100 they have. 91 is available from different pumps. Not sure why they put in 87 with all these though.

 

[Dave1027]

I quit using 87 octane years ago. Got tired of my vehicles running like crap like stumbling and pinging. Been running 89 ever since and all vehicles run very well like brand new. I'll pay a couple a bucks more for peace of mind.

 

[HoosierJeeper]

My LR seems to like 91 or 93 better for more demanding conditions, but the Liberty especially runs better on 87. Manual says to use 87, can use 89 in hot weather or towing, but 91 will decrease performance.

 

[Dave1027]

Originally Posted by HoosierJeeper
but the Liberty especially runs better on 87. Manual says to use 87, can use 89 in hot weather or towing, but 91 will decrease performance.
That's impossible.

 

[maintenanceMan]

Dave, this is not impossible. Often Ethanol is used as the octane improver. Ethanol has a lower btu content as compared to gasoline. Most of these engines that run better with slightly higher octane, very likely have small deposits inside the combustion area that raise the compression ratio. This necessitates higher octane to run correct timing.

 

[litesong]

Some short things to clear up about octane "definitions" for gasoline engines. First, gasoline engine engineers know what they are doing, when designing say, 87 octane gasoline engines. Therefore, when using 87 octane, ethanol-free gasoline(E0) in 87 octane designated gasoline engines, the most efficient results occur.... because 87 octane E0 gasoline IS 87 octane. Second, gov't forces designated 87 octane ethanol blends(E10) into our engines. However, the ethanol component is 114 octane. PLUS, the gasoline component is 84 octane, to arrive at mathematically designated 87 octane ethanol blend. Yes, none of the components of 87 octane designated E10 are 87 octane. That is why burning 87 octane E0, in my last five 87 octane, low compression ratio gasoline engines, over decades of use, have given 8%, 8%, 7%-8%, 7%, & 5% BETTER MPG than 87 octane designated E10 ethanol blends, which are used, but NOT burned efficiently in 87 octane designed gasoline engines. In addition, 87 octane E0, burned efficiently in said cars, are smoother, quieter & have "slightly" higher torque at low rpms, such that less down-shifting is needed, when ascending gentle hills with good feather footing techniques.

 

[Whimsey]

Our 2017 2.3 EB Explorer requires at least 87 octane but 91 or higher if you want the "full" performance or if you tow and drive in high temperatures. We bought it new in early Feb 2017 and ran 93 octane through August of 2017. That included some winter/spring driving in NJ and a trip to Key West in June and Tenn in August. From Sept 2017 through now we've been using 87 octane only. This included another trip to Key West from NJ in June 2018. Gas mpg gain with 93 is at best within any margin of error, very little. When needing rapid acceleration on the highway it did perform slightly better with 93 vs 87. Over all the benefit of using 93 vs 87 is not worth the $.50-$1.00 per gallon more for the 93 octane. 99% of the time we use top tier gas, mainly Shell. If your vehicle requires premium fuel than by all means use it. But this is just my real world experience with this vehicle. The compression ratio for this engine in this vehicle is 9.5:1, not high at all.

Whimsey

 

[WishIhadatruck]

At some point I've tried 93 octane in every car I've owned. I never noticed a difference in power or fuel economy with the exception of my 2014 Cruze Eco MT. Below 32 deg. F, it would be hard to tell the difference, but the warmer it gets, the more it prefers higher octane. I typically run 89 octane when it warms up in the spring, once it gets over 70 deg. F, I run 93 octane. I get better fuel economy and the engine runs much smoother. If you have 87 octane in it during the summer months, on a hot day pulling into traffic, it can feel like you're running on 2 cylinders. As the turbo starts to kick in, you'll have power, then all the sudden it pulls the timing and boost and you are left with very little acceleration. To the point I would call it a driving hazard as you never know if you can pull into traffic or not. With 93 octane, it runs great. Kind of annoying as it is supposed to be able to run on 87 octane per the manual.

 

[ofelas]

I found the same as HoosierJeeper did, but on a 2003 Liberty 225ci.

As long as the combustion chamber/piston tops are clean, there's no benefit to running higher than the minimum spec'd octane rating on a vehicle without a knock sensor, unless it's to gain the benefits of an ethanol free fuel.

That vehicle now uses ethanol free 87 from a small, clean independent. I prefer my rubber to last longer, the fuel to absorb less water, and the albeit small increase in BTU of ethanol free fuel.

Originally Posted by Dave1027
Originally Posted by HoosierJeeper
but the Liberty especially runs better on 87. Manual says to use 87, can use 89 in hot weather or towing, but 91 will decrease performance.
That's impossible.

 

[y_p_w]

Originally Posted by maintenanceMan
Dave, this is not impossible. Often Ethanol is used as the octane improver. Ethanol has a lower btu content as compared to gasoline. Most of these engines that run better with slightly higher octane, very likely have small deposits inside the combustion area that raise the compression ratio. This necessitates higher octane to run correct timing.

Worse with 91? Highly unlikely that lower octane rating would result in worse performance - ethanol or not. And certainly in today's market almost all regular contains ethanol (maybe MTBE in some states) as an oxygenate and octane booster.

The name of the coast common commodity fuel in the US is RBOB (reformulated blendstock for oxygenate blending). It's meant to be 87 (R+M)/2 when combined with 10% denatured ethanol.

Deposits are far likely today given that there's a mandator requirement for fuel detergent, and especially less likely with most of the major retailers signing on to the Top Tier standard. The testing requirements mandate at least 8% ethanol in the test fuel, so the efficacy has an ethanol blend in mind.

 

[litesong]

Originally Posted by maintenanceMan
Ethanol is used as the octane improver.
As stated in my post above:
"......when using 87 octane, ethanol-free gasoline(E0) in 87 octane designed gasoline engines, the most efficient results occur.... because 87 octane E0 gasoline IS 87 octane."
114 octane ethanol can NOT "improve" octane, better than 87 octane ethanol-free gasoline (E0) burning in 87 octane designed gasoline engines.

 

[ofelas]

I believe MaintenanceMan was (correctly) referring to ethanol being used to boost a lower octane gasoline up to an 87 rating at the pump.

A farm subsidy at it's best.

 

[y_p_w]

Originally Posted by WishIhadatruck
At some point I've tried 93 octane in every car I've owned. I never noticed a difference in power or fuel economy with the exception of my 2014 Cruze Eco MT. Below 32 deg. F, it would be hard to tell the difference, but the warmer it gets, the more it prefers higher octane. I typically run 89 octane when it warms up in the spring, once it gets over 70 deg. F, I run 93 octane. I get better fuel economy and the engine runs much smoother. If you have 87 octane in it during the summer months, on a hot day pulling into traffic, it can feel like you're running on 2 cylinders. As the turbo starts to kick in, you'll have power, then all the sudden it pulls the timing and boost and you are left with very little acceleration. To the point I would call it a driving hazard as you never know if you can pull into traffic or not. With 93 octane, it runs great. Kind of annoying as it is supposed to be able to run on 87 octane per the manual.

There are cars these days that specify 93 (R+M)/2. I remember when I was looking through my WRX manual it said that 93 was the recommendation for the STI. Same for most Porsches. The new WRX says it will take advantage of 93 but it can also use 87 without damage.

It was years ago but I remember getting in some long-winded Usenet discussion with someone arguing about not relying on knock sensors on the premise that engines self destructing was a serious possibility. But these days we deal with that - especially flex-fuel capable engines that will go to extreme timing advance to take advantage of E85.

I also remember seeing a video of a guy taking delivery of his Honda Civic Type R at the factory at Swindon (I guess there's more news on that place). He went on the standard test they ran on their closed course and talked about it with the Operations Manager of the Swindon factory. The manager was talking RON. Not sure if these two aren't properly accounting for the (R+M)/2 that we use in the US and Canada, but I think it's easy enough to look up even though it's really approximate. In the end I believe the ECU will just map it to what it likes since it has no idea what the octane rating is or what scale it's sold under.

Quote


Fuel. Fuel is the main difference. Obviously in the states you're not running at the 98 RON level. Over here we run 98 RON in nearly every fuel station you go to. So this engine is tuned at 98 RON. So the ECU is mapped in that way. But I think if a higher octane fuel is used in the car in the States then you'd have similar power output. And it would remap automatically.

And it's set up for 99?

Maximum.

So if we run like 104 octane at race spec in the US. We ran 104 it wouldn't do any more for it.

No.

It maxed out at 99.

Yep. Yep.

 

[ofelas]

Informative post, but you got me at "Type-R"

 

[pkunk]

I've noticed that all of you saying you need the higher octane fuel live at sea level or just above. Here, where 99% of my driving is above 7000ft I get better economy & power with 88 octane in my vehicles that 'require' premium. Altitude is a game changer.

 

[Malo83]

Run 89 in both my 08 Malibu v6 and 83 Silverado, 91 in my 2017 regal GS

 

[diyjake]

I always run Top Tier 87 octane and works great for me. I think the key is not higher octane but the quality of the fuel.

 

[y_p_w]

Originally Posted by pkunk
I've noticed that all of you saying you need the higher octane fuel live at sea level or just above. Here, where 99% of my driving is above 7000ft I get better economy & power with 88 octane in my vehicles that 'require' premium. Altitude is a game changer.

Depends. Altitude most definitely robs power, but the reduced pressure means lower pressure inside the engine and less demand on the octane rating unless there's forced induction. I know some places up in Colorado used to sell lower octane rated fuels on that premise. Something like this: