I've just purchased a new vehicle, any thougts on switching over to a full snythetic -----O-W -30 to optimize fuel economy. The manufacturer claims their product improve economy. Your thoughts on this claim ?

In my opinion, the single most important preventive maintenance step is to use full-synthetic engine oil and full-synthetic transmission fluid in your vehicle. I go further and only use synthetic power steering fluid and synthetic grease. The links below summarize my thoughts:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563.html#post219991

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563.html#post220276

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-11.html#post2059400

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-7.html#post1114610

Using synthetic engine oil and transmission fluid will increase gas mileage 8 to 10%. The biggest mileage improvements are achieved by using synthetic transmission fluid, differential gear oil, and wheel bearing grease. These items have the greatest friction, to begin with. Drive your car from the showroom to the service bay and change these fluids right away. You'll be glad you did.