06 Montero Ltd Gen3 - is premium fuel necessary?

[plh]

I may have been wrong. There is reference in the '06 FSM about a knock sensor. Never believe the internet. Anyways, I've run "Premium" a few times over the 100K miles of ownership. Can't conclude it makes a difference. Driving style makes more of a difference in MPG (typically 17 to 19mpg highway, wind, speed, terrain, driver - dependent), variance in fuel type is hidden. In the upper midwest it costs 20% more $$ for this fuel. I'll stand by my original statement Premium is not required. IIRC the label says " Premium Fuel Recommended". Pure marketing hype.

I would be more concerned about using a top tier fuel and freshness. Mid grade premium and above grades sell combined at about a 12% rate of regular. Who knows how long the specialties have been sitting around at your local fill-up spot.

 

[Salonika]

I may have been wrong. There is reference in the '06 FSM about a knock sensor. Never believe the internet. Anyways, I've run "Premium" a few times over the 100K miles of ownership. Can't conclude it makes a difference. Driving style makes more of a difference in MPG, variance in fuel type is hidden. In the upper midwest it costs 20% more $$ for this fuel. I'll stand by my original statement Premium is not required. IIRC the label says " Premium Fuel Recommended". Pure marketing hype.

I agree......I’d say the only way you would see a difference is on a dyno.

 

[tj90]

When I first got my montero 03, I did a test. I ran a full tank of premium and a full tank of regular from same tier one gas station (chevron I think). I tried to match the drive conditions perfectly on my commute in light to no traffic on both tanks. I averaged the timing advance over several consecutive runs on the same fuel. I monitored the timing advance in real time and collected the data. I found that the two fuels did make a big difference in timing advance. It was on the order of 5-10 degrees of advance. The premium was allowing the engine to delay detonation to achieve maximum compression. Another advantage is that I found my MPG to increase on premium 2-3 mpg. To me, the difference in cost (~10% at the time) was made up for better MPG (~20%) and more power. The money you save with regular unleaded is false economy. You are really losing more with poorer MPG and lower power. I did this test 10 years ago and Im not sure if any of this is true with 250k miles on the ODO. I dont worry about it and just put in premium. Premium is good for older engines, because it provides better knock protection (pre detonation) on older engines with carbon build up.

 

[coffeegoat]

After seeing the improvement with my new O2 sensors (butt dyno and MPG), I'm curious if a bunch of the "I never saw any improvement" comments (mine included) are because other stuff in the fueling system is not operating optimally so the system isn't running where it should. These trucks are getting old and some of my research on O2 sensors indicates they start giving poorer (not wrong, but not great) readings after 10 years or so. Figure in some dirty injectors, maybe a bad air flow sensor and pretty soon all of the potential benefits of higher octane fuel disappear. I wish Torque or other apps would make it easy to output a bunch of average values so you could more easily compare with other vehicles of the same vintage, it seems this is a bit of a dark art where it doesn't need to be.

 

[taybrynn]

Rockauto sells a knock sensor for the 2006 montero.