AutoMechanic
Site Donor 2024
I’m not too sure what RON is?
Hybrids and 91 Octane Gas?
- Thread starter hytibilly
- Start date
RON = Research Octane Number, just a different way to measure octane. Not used here in the U.S. but over in Europe this is what is used.
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From my experience most modern vehicles will benefit from higher octane gas is certain situations. I have a few examples from my own vehicles I've owned. I log most of my vehicles using the torque app on my phone.
Used to own a 2009 Malibu LTZ with the 3.6 V6. 87 octane gas was recommended but 89 was mentioned in the manual for max performance. That 3.6 performed better under all circumstances with 89 octane in the tank. My average MPG was up by almost 2, and the transmission shifted better because the torque management (timing retard) was much less intrusive when shifting.
My 2012 Buick Regal GS recommends 91 octane across the board. It performs better in all conditions in the event I can find a gas station with 93 octane. When logging with my torque app, timing advance is more stable, mass airflow in increased from an average of 202-207 g/sec and 17-19 psi boost with 91 octane, to a consistent 217-221 g/sec and 21-23 psi boost with 93 octane in the tank. This is a significant change in the seat of your pants.
My 2005 GMC Sierra has the L59 which is the 5.3 that is E85 capable. I have done pretty extensive testing with fuel grades with this truck while towing and despite the recommendation from the manual which says nothing more than 87 octane is needed I can confirm that higher octane gas does provide significant advantages while towing. All the stats below are done with the same trailer (3500 lbs or so) where temperature and wind changes were kept as consistent as possible.
87 octane. While monitoring timing advance while towing in 4th gear at roughly 1600 RPM (60 mph) timing advance will maintain about 15 degrees advance before requiring a downshift. MPG achieved during a longer loop drive was 13.2 MPG hand calculated.
91 octane. Same loop and conditions described above. Timing advance was maintained at 21-22 degrees before requiring a downshift at 1600 RPM at 60 MPH. MPG achieved during this loop which was the same as the loop with 87 octane, mileage was 13.9 MPG hand Calculated.
E85, Same loop and conditions described above. Timing advance was maintained at 29-31 degrees before requiring a downshift at 1600 RPM at 60 MPH. MPG achieved during this loop, which was the same loop as previous, was 11.1 MPG hand Calculated. Noticeably more power and better gear holding ability was experienced with higher octane and timing advance. All with an engine with 9.5:1 compression.
Seeing as how I only experienced a 16% reduction in fuel mileage with E85 compared to 87 octane while the change in price between 87 and E85 hovers around the same percentage around these parts, it actually makes economic sense for choosing E85 while towing with this rig, especially considering how much better then engine performs making for a more enjoyable experience.
If anyone bothers to read all that, the point is, on hot days even if a vehicle recommends 87 octane, give higher octane gas a shot and see if it makes a difference and then do the math to see if it makes sense to your pocket book. This post is about hybrids but it applies to any modern vehicle.
Used to own a 2009 Malibu LTZ with the 3.6 V6. 87 octane gas was recommended but 89 was mentioned in the manual for max performance. That 3.6 performed better under all circumstances with 89 octane in the tank. My average MPG was up by almost 2, and the transmission shifted better because the torque management (timing retard) was much less intrusive when shifting.
My 2012 Buick Regal GS recommends 91 octane across the board. It performs better in all conditions in the event I can find a gas station with 93 octane. When logging with my torque app, timing advance is more stable, mass airflow in increased from an average of 202-207 g/sec and 17-19 psi boost with 91 octane, to a consistent 217-221 g/sec and 21-23 psi boost with 93 octane in the tank. This is a significant change in the seat of your pants.
My 2005 GMC Sierra has the L59 which is the 5.3 that is E85 capable. I have done pretty extensive testing with fuel grades with this truck while towing and despite the recommendation from the manual which says nothing more than 87 octane is needed I can confirm that higher octane gas does provide significant advantages while towing. All the stats below are done with the same trailer (3500 lbs or so) where temperature and wind changes were kept as consistent as possible.
87 octane. While monitoring timing advance while towing in 4th gear at roughly 1600 RPM (60 mph) timing advance will maintain about 15 degrees advance before requiring a downshift. MPG achieved during a longer loop drive was 13.2 MPG hand calculated.
91 octane. Same loop and conditions described above. Timing advance was maintained at 21-22 degrees before requiring a downshift at 1600 RPM at 60 MPH. MPG achieved during this loop which was the same as the loop with 87 octane, mileage was 13.9 MPG hand Calculated.
E85, Same loop and conditions described above. Timing advance was maintained at 29-31 degrees before requiring a downshift at 1600 RPM at 60 MPH. MPG achieved during this loop, which was the same loop as previous, was 11.1 MPG hand Calculated. Noticeably more power and better gear holding ability was experienced with higher octane and timing advance. All with an engine with 9.5:1 compression.
Seeing as how I only experienced a 16% reduction in fuel mileage with E85 compared to 87 octane while the change in price between 87 and E85 hovers around the same percentage around these parts, it actually makes economic sense for choosing E85 while towing with this rig, especially considering how much better then engine performs making for a more enjoyable experience.
If anyone bothers to read all that, the point is, on hot days even if a vehicle recommends 87 octane, give higher octane gas a shot and see if it makes a difference and then do the math to see if it makes sense to your pocket book. This post is about hybrids but it applies to any modern vehicle.
Actually the RON number is used, but in a different way. In the formula ((R+M)/2) or 87 the R is the RON (research Octane) + M (Motor Octane number) divided by 2. Here in the US that usually means 87 Octane as the number you see on the pump.
According to motortrend, your 5.0 makes 407 hp and 372 lb-ft on 87, so 13hp and 11 lb-ft less, something you definitely wouldn’t feel even in a highly calibrated butt dyno.
The issue will always be that premium is just so much more $$ than regular that any slight benefits in performance or efficiency are never recouped by average drivers using their cars in average ways. Here I regularly see the price differential upwards of ~$0.80+. I run premium in my car that runs aftermarket software that requires it, the other 2 get 87 and even our Lexus that says premium just gets 89.
Nick1994
$100 site donor 2024
Ah, I hadn’t seen numbers comparing the two.
I think the next couple tanks I’ll run some 91 and see how it goes just for the heck of it.
My Toyota Prius says 87 Octane and at 94K miles the car runs flawlessly. I've never run 89 in the car but other Prius owners have said they saw no increase in fuel mileage when they did. My Volvo says minimum 91 octane and there is a major difference in fuel mileage and performance if I run 89 or 87. I use the car exclusively on the highway and fuel mileage takes a major hit with 89 and 87. Normal highway mileage runs north of 28 mpgs with 91-93 octane fuel. 89 Octane will drop the fuel mileage into the 24's and 87 will take it into the low 22's or high 21's. Yes it is that bad of a hit. Needless to say that fuel economy test lasted exactly one tank of gas for 87 and 89 octane.
I run 87 in my 420hp Genesis
Direct injection vs. conventional injection.
OVERKILL
$100 Site Donor 2021
Yes, I expect that plays a role for sure. My wife's 395HP HEMI "recommends" 89 but says 87 is acceptable. It is also traditional port injection.
You buy a hybrid to spend less on gas. Why toss that benefit away and pay more for higher octane if the engine doesn't need it?
Right. Before (R+M)/2 became a thing, Research Octane was the number that usually came up in discussions and owner's manuals. The so called "Research" and "Motor" ratings are based on two different test procedures. Both procedures have been around for many decades. Supposedly (R+M)/2 correlates better with knocking tendency in modern engines than either one.
One of the local Toyota indies advises against using anything higher than 87 in a hybrid for the risk of excessive carbon build up that can trigger a delayed start DTC/no-start condition. But the Lexus GS450h/LS600h call for premium as well. higher octane fuel does burn slower but I can’t see that attributing to excessive carbon.
the rule of using the recommended fuel grade still applies.
the rule of using the recommended fuel grade still applies.
wemay
Site Donor 2023
87 is recommended for both GDi Turbo vehicles in my signature. Have tried 93 but noticed no difference in economy or power. Maybe there was, but we couldn't tell.
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My 2010 Toyota Prius, specifically called for 87 octane, and said anything higher was a waste. In 11 years, the 2 times I used 91, there was absolutely no difference in performance or mileage.
Lexus RX450h wants crappy CA 91 wannabe premium.
My old '66 GTO wanted Sunoco 260 superman premium.
My old '66 GTO wanted Sunoco 260 superman premium.
