Worse mileage with synthetic (and Bosch Platinum +4's)?

[hooah212002]

I just did my first oil change since getting my car. I put Mobil 1/5W-30 in. I also changed the plugs to Bosch Platinum +4's. I haven't yet went through a full tank, but it seems as though my mileage is worse (so far anyways). I usually get 330ish miles per tank (10gal). I am close to half a tank now and only at 120 miles. How is this possible? I do notice a slight performance increase, but I don't use it. I still drive 60-65 on the highway portion of my route to work (80% highway), and pop it in neutral almost always before coming to a stop.

[petrified.rabbit]

Get rid of the platnium plugs

[petrified.rabbit]

Also coasting in neutral uses more gas than decelerating the car. Because the car is fed gas at idle versus cutting fuel until reading the matched rpm according to the pedal (with the momentum of the car keeping rpms above that point). But this is nitpicking onfuel consumption maybe a mile per tank.

My car always has it's best mpg right after an oil change and even feels a little more powerful. But I use conventional as the only reason for synthetic is factory tolerance recommendations and/or to prevent sludging typical in low displacement turbo engines. Even though synthetic is typically benefiticial across the board, I have found in my "cheap" cars it doesn't make a big difference like onewould expect. Especially for the added cost.

[dleebold]

from what i've read on other post,the aveo motor doesn't play well with platinum plugs.copper core plugs do.

[Thymeclock]

I never had any use for platinum plugs. Conventional plugs work fine. Check that you have the correct heat range for whatever plug you are using. If it is too 'cold' a plug your mileage will be affected. Also check the plug gap.

The synthetic oil shouldn't make any difference, but the plugs would.

[hooah212002]

Also coasting in neutral uses more gas than decelerating the car. Because the car is fed gas at idle versus cutting fuel until reading the matched rpm according to the pedal (with the momentum of the car keeping rpms above that point). But this is nitpicking onfuel consumption maybe a mile per tank.

The folks over at EcoModder may be privy to that info. There is an entire community who seems to think just the opposite.

[petrified.rabbit]

look at apr tuning chips, they completely cut fuel on deceleration to improve fuel mileage. their research is better than mine,

[MetroMPG]

Coasting in neutral while idling can be more beneficial than decelerating under fuel cut when the coasting distance is significantly longer. Under fuel cut, you're engine braking, so not going to go nearly as far. Meaning you needed to stay on the gas longer before beginning to engine brake, or get on the gas sooner after engine braking (unless you're coming to a full stop).

There are times where each approach is more efficient. But you're right, the difference amounts to drops in the bucket.

One instance where fuel cut is desirable over neutral coasting is where you want to slow down faster than a neutral coast. Definitely less fuel used with fuel cut/engine braking than by using the friction brakes in neutral.

[Rotareneg]

On my '07 Aveo (with a manual,) the engine will not enter fuel cut-off if I let off on the gas while going less than 40 MPH, regardless of the gear I'm in. Starting at around 42 or so it'll work, and stay in fuel-cut until around 1200 RPM.

[MetroMPG]

Rotareneg - how are you monitoring fuel cut mode?