fuel grade

[alancameron]

what damage to engine if i use grade 95 and

manufacter recomends 98

[KebabMeister]

First of all, what type of car is it and what year was it made?  Is it designed for unleaded fuel?

It shouldn't cause a problem because 95 RON is a lower octane rating (refined) to 98 RON; you'll notice a loss in performance. 

So, does it run on unleaded or leaded fuel (or LRP!)?  In extreme circumstances you may have to change the ignition timing.

[Impret-Sir]

Alan, your not running an Impreza by any chance are you? These are reccommended by Subaru to be run on "super" unleaded, but many owners, including me, run them on "ordinary" unleaded. As KebabMeister says, you will notice a very small reduction in performance, (worth it for the cost saving IMO), and should do no damage, after a short while your engine management chip will adjust timing etc to allow for the lower octaine rating.