Use of Premium Petrol to get better MPG
 

I just wants to share my experience. I have a Suzuki Swift 1.3 L (small) Automatic.

I have been experimenting with normal (90 Octane) , High Octane (95) as well as Premiums Friction buster (93).

With the normal (90), the vehicle needs to reach above 60-70 km/h to come to overdrive (4TH). With the high octane petrol, the engine respond quickly and can reach the overdrive between 50-60km/h.

I have been getting better mileage from 10 kml/l at the start and now above 12.5 km/l . Off course there is definitely a improvement in driving method.

My point is with automatic gears, it is difficult to change in to 3rd 4rth gears. If we can manage to keep the vehicle in higher gear, the MPG will go up. Therefore if we can try to move the gears to higher gears by driving, fuel variations (octane and additives), engine friction reducers, avoiding higher loads such as AC, over weights, we will be able to get better results with Automatics.

Of course I am using kind of light throttle, which quickly change gears than heavy throttle. There are times this is not possible such as climbs, running with AC and Heavy loads etc.

The High octane will definitely gives lower energy, but this is not about energy, but the engine response. So that CPU thinks that engine is running at a higher speed with lower throttle and lower load so that it jumps to the next level.

This may not be a good theory, but I see a improvement. However maintaining this is not an easy task as traffic patterns, road conditions, outside temperature, no of passengers and the weights etc.

Any thoughts?:rolleyes:

CWA

I drive an automatic too, and if you think that your 1.3 liter is small, you would be blown away by my .660 liter!! It is a kei car, only available in Japan, and it is a three speed. I get around 23-25km/l in my little guy. Course I use lots of EOC and I don't have many stops in my route. I get into 2nd gear at 20km/hr and I force the car to shift up to 3rd at 30km/hr. 2nd gear is pretty finicky, and won't engage at anything less than 20km/hr, but I can play around with 3rd a little depending on conditions. 25km/hr is about the lowest I can force the car to shift into third at.

I always put in regular for my car, but going off of what you are saying, maybe I should give high octane a go. My company pays for it anyways...

Sounds like the shift point is tied into the ignition timing and the higher octane is advancing the timing more making it "think" you have less load on the engine and causing it to shift sooner. Interesting effect . . . I wonder how tire pressure would affect the shift points?

It's a sensible concept. The higher octane provides greater torque at lower rpm with more aggressive timing - requiring less fuel and air for the same net torque. This has the effect of preserving more vacuum - which as most of us know is a large part of determining shift points in automatics. I.e., more vacuum means earlier upshifting.

Nice! :thumbup:

I should add that this will really only work if your engine computer is capable of advancing timing to take advantage of the higher octane. People with carbureted automatics are unlikely to see as much if any improvement unless they are already running aggressive timing.

Tested with No Advantage
 

I tested this on the Automatic 'Teg with no perceived advantage over 87-octane.

Other factors may have been at work with a high intake air temp, etc. Engine knocking was not noted with either fuel, so the change back to regular unleaded was a better choice financially.

The only hard data I have is the Gaslog.

The inverse is true for engines that require premium fuel. A single-blind study in the TSX (fancy for "put regular fuel in my Wife's car without her knowing :p ) showed that premium fuel, as required for the higher compression, resulted in an average of 2 mpg higher than the cheap stuff. 28.x vs. 30.x

YMM will probably V

RH77

Since we're talking km/L, well my lifetime average is about 26 km/L, without trying....

I would think that any car with a knock sensor would benefit in various ways from higher octane fuel. Cars without one would probably not see much of a difference.

Thank you Snax,

My car has VVT and also it has a slightly higher compresion ration (9.5). I have noticed that car responds very well to higher octane fuel. As Snax pointed out, I feel I get get the sufficient torque without a higher throttle and Higher fuel burning.

This may be applicable for certain type of vehicles with FEI, VVT, etc?

CWA

Would seeing higher maximum ignition advance figures on a ScanGauge in normal highway driving when using higher octane be indicative that there is at least some advantage?