I say you'll be just fine. It appears to meet the OEM requirements, and it will be fine in your climate. The fuel economy penalty will be negligible, if non-existent, and certainly won't be measurable outside a lab. Heck, an ILSAC 10w-30 and ILSAC 5w-30 can have identical HTHS, so any fuel economy benefits of a 5w-30, for instance, might only be during warm up. The 5w-30 I'm running will be worse on fuel economy than the 10w-30 you have, but I'll never measure the difference, either.