Is unleaded 91 what its supposed to be

[REDRODY]

I own a '99 V6 rodeo and have to drive up a fairly steep grade to get home.
I have always used unleaded 91 with no problems.
Recently I have noticed it pinging a little while climbing the hill home so after doing some reading on fuels decided to try Caltex Vortex 95 and guess what no more pinging.
This has got me thinking - since the price of fuel of late has jumped about 30% in price is unleaded 91 actually 91 or have the fuel companies kept it on the "lighter side" of 91 to save a buck.
It may be a coincidence and my hearing has suddenly got bad as to not here any pinging but?
What do you think.

[Tree cutter]

It could be a dirty fuel filter causing your engine to run a bit lean under load so it pings. It could be just crap fuel too.

[Pigdog]

Or a timing issue.

[Chuckanoo]

Check your oil!

I had the same problem when I used to own a 2wd:o
After changing to a different brand of oil (but same viscosity), the pinging disappeared:thumb: