I ran 87 for months on my LPT with it's stock turbo. Premium made absolutely no difference. You're not making enough boost for premium to be a requirement.
87 is the minimum recommended octane for your vehicle. (per the manual) Premium certainly would not be required on a naturally aspirated S60, and it most likely wouldn't feel much different. Even if it did, wouldn't you rather have a little extra money in your pocket, given that it isn't a performance car?
Tune your XC, then you'll begin to see a need to upgrade the octane.
I ran 87 a few times just for kicks on my ARD tuned 15G LPT. It ran a few PSI less boost, but still pulled hard and ran great. These cars are not dumb, and you're not hurting them in any way. Even Lucky (the tuner) said that if 87 was used on the 93 octane map, I'd be totally fine... it'd just be a little slower.
If you ran 93, you'd still be running a paltry 5-6psi on the little 13T. (No different than if 87 was used)
87 is good for your needs... especially if you're not an aggressive driver. The best way to decide what one to use? Try 87 yourself for a week or two. Once you're in the habit you may see higher grades were a waste.
I don't know... i guess it's a matter of preference I just think it's better for the car and I get more miles per tank so idk. As for the first car I can't expect to have a freaking 300hp car.. but it's about time to get something around there, time for a change gonna be 2 years in April since I got the car, I kinda wish it was the 2.5t and then I'd be satisfied... it has a lack of power but oh well life goes on haha
Premium is totally not necessary for an LPT
I've found that 89 is just fine (I use 89 in all my personal LPTs) for YEARS
While 87 won't hurt it, it won't run quite as well and 91-93 does NOTHING except to your pocketbook
for LPT you don't need premium, as stated. Hell, even a stock R could really run fine at 10psi and 87octane, though not advised.
When I had the 15psi IPD tune on my '98R my father though it okay to put 87 in...you know what, it ran okay, just fine, except wide open throttle and max boost, it would get a misfire. THAT is where you can't run lower gas with higher boost.
The higher the octane rating of the fuel the more resistant it is to pre-ignition and being the cause of engine knock, which in turn becomes safer as rpms and ambient engine temperatures rise. I can go more in depth tonight when I get home from work.
If you decide to get feisty and max out your stock engine on say a 19t or so, C16 might be a decent fuel to start with. E-85 is an amazing fuel for high horsepower applications because of its tolerance to knock as well. 87 burns hotter than 91, 93 which makes it more volatile to pre-ignition and a less desirable fuel source. The opposite of this is when you do not gap your spark plugs correctly for the application and you get blow out, which is usually followed by a cylinder being soaked in fuel and a nice pop from detonation.
And Endwell huh, that is about an hour and a half south of me. I've been there many times. Once I get the turbo back in my car and the intercooler piping sorted out I'd like to meet up with fellow Volvo owners.