I am planning a 2000 mile trip with no load. Can I use plus gas 89 octane inastead of the super unleaded with no incidence? I figure I'll save about 15 cents a gallon. I am almost never into the turbo boost all the way. The engine is a 1994 "L" turbo engine in great shape.
Does anyone ever use regular gas in the turbos with any ill effects? Just wondering if paying for premium is worth it. Once I tried plus 89 octane instead of 91 and I heard a very slight pinging up a freeway hill on a hot day but I backed down with no problem.
Anyone have experience here with gas grades. I usually just put in the "best" without thinking, but I wonder if its really worth it if you don't drive it hard. Does it hurt the internals at all, or is the knock sensor good enough to keep things safe?

It will do fine. The knock sensor will keep all in check, it will retard the spark which will decrease power & efficiency. It is a trade-off, will the decreased mileage outweigh the cost savings for fuel? I never ran the numbers so cannot say for sure. I have run all grades in my '94 945T with no ill effects to the engine, it has 280k+ miles on it.

Like others, I use 87 octane in my '86 745T. I have for probably the last 15 years and 80,000 miles and never noticed any ill effects.

Pinging in a turbocharged engine is very bad. You may want to have it checked out.

I use 87 in my '90 765T, except when towing in the summer.

My dad runs regular in his 1995 945 Turbo, and it seems to do fine.