95 vs 98 octane: Fuel consumption test

[goseatonio]

Time to time, we read in forums different opinions ensuring that using 98 gasoline, the consumption is lower.

During out trip to Ireland, we crossed France, and then we decided to do a comparasion test between 95 and 98 in order to know the truth.

For the test, we used two Mazda MX-5 1.8 126cv Soft Top Active+

Car A: 2009 model, tyres Bridgestone 205x16" 2.0 bar

Car B: 2008 model, tyres Michelin PS2 205x45 17", 2.1 bar

Test stardet in the last petrol station before entering France, the route ended in Le Mans, 99% french autoroutes, at maximum legal speed (130km/h). Both cars top up, automatic clima at 22º.

We made two stages:
First stage car A used 98, and B used 95, then, when reserve light get on, we interchange the kind of petrol, and did the second stage.

Results:

First stage: 541 kms
Car A: (98.oct) 40,5 litros (7,48 litros/100kms)
Car B: (95 oct.) 39,8 litros (7,36 litros/100kms)

Scond stage: 485 kms
Car A: (95.oct) 38 litros (7,83 litros/100kms)
Car B: (98 oct.) 37 litros (7,62 litros/100kms)

Average comsumption after 1.026 kms:

Car A: 7.65 litros/100 kms
Car B: 7.48 litros/100 kms

98 octane: 7,55 litros/100 kms
95 octane: 7,58 litros/100 kms

Diference of compsumtion between differnet octanes: 0,4%


We think that the different in comsumption is so small that, maybe the causes could be small differences when fuelling

[sifpilsen]

These kind of differences can come down to the drivers as well. How you react to maintain that 130 km/h speed in slight hills up and down, could affect the consumption too. It shows either driver in car A is slightly more agressive on the throttle, or luggage/passenger weighs more

But as you say, the variance is too smal to actually find a difference. Next: rallyfuel vs 95, on track, lap times to decide

[Steve]

so 37.2 vs 37.4 mpg? It would be nice to get that kind of mileage

[goseatonio]

As sifpilsen said, the differences are too small to have in consideration.

A performance test would be hard to perform, but I've read a test some months ago in a spanish car maggazine, and they didn't found any difference in performance or power in cars designed for 95 when using 98.

I didn't know that in Ireland you calculate the consumption in mpg, sorry, anyway, I think is not a bad milleage cruising at 130km/h 2 passengers, full luggage and AC connected. When I use my car daily or having fun in winding roads, the mileage is not as good.

[sidewaysreilly]

It would make no difference at all unless 1: you are running over 11:1 compression or 2: you are turbo/supercharged.