Just got my new car and it's this one.

so far so good except door seals maybe weak? feeling a draft usually.

Called Buick to see what to expect for this service-check and was told the following. I was also told that the previous owner didn't do anything but oil changes on it.

CANADIAN FUNDS.

coolant flush ~100
injector flush ~100
tune-up ~240

My friend told me coolant would make sense to be done at the start of summer...no worries about it now.

Also, to just buy a bottle of injector kleen or the like and bypass injector flush.

Tune-ups a tune-up I guess I need that?

I'm a first time full-time driver., so I don't know what norms are HELP. for example, does it hesitate, is mileage good/bad..etc.

Also doing 90km/h HWY I've done 380kms and it's just below 1/4 tank. That sound right to people? Shouldn't it be way more than that???

For the mileage, I would expect a lot more, assuming you've got a 15 gal tank. I roughly converted your km to be 237 Miles (I like kilometers, but with fuel economy I can only think in miles, sorry!), and if you're at just under a quarter tank, we'll assume you've got about 2.5 gallons left. With that, it means you're averaging about 19 miles to a gallon. For a regal, that's not bad at all for city driving, but for highway (especially at 56 mph) I would expect it to be a lot better! (Maybe about 27 to 29 mpg).
I would wonder if its not shifting up into fourth gear, or if your torque converter isn't locking up. At your highway speed, does it feel like it's doing high RPM's?
Hopefully someone else around here has some ideas!
Good luck!

Well I called Buick....rather GM..and I was told

for this vehicle. it's 7.3km/L HWY & 12.5ish Km/L City....so

I figure on a 66L tank the HWY driving would be about 462kms...which from my 430 test going 90%HWY at 90km/h is fairly good enough considering it's age....

but to consider for a moment that city driving should yield me 792ish Km'sWOW.....that's impressive...though highly impossible to achieve.