at 7.8 its obviously better than 9 on 95 so it does make a difference using 98 with a saver docket its better i got800 from one tank and it still only took 65 litres to fill
with 98 i have got the car down to 7.9 on the highway from sydney and the higher the octane the better the mileage ive used e 10 and that is crap just watch your av go up you can notice the diff but i also use 95 depending on price
even from a dealer you will get remainder of any factory warranty also check out fowles lots of ex gov cars camry 4 cyl 2005 were going for 10 to 12 grand and they had heaps
my advice as a tyre fitter would be not to worry about tread pattern as the bigger block patterns are often noisey silica is good not bad just dont buy performance tyres falken are good