Nissan Repair: oil change yeild worse milage, nissan d21, z31 300zx

Question
Hello Calvin,

I have a 92 Nissan d21 se-v6 and I recently did an oil chane on it and I had accidently grabbed 10w40 as opposed to 10w30 like usual and now my mpgs are down and I'm at a loss. I have checked all my plugs and points and my air filter and they're all good til my next oil change/ tune up. I'm wondering if the thicker oil could be why my fuel mileage is so low. Also, I am wondering if a shifter from a z31 300zx would fit and function properly in my truck(it is a 5spd)?

Thank you,
Shane

Answer
Hi Shane -

This seems unusual to me. Normally if anything changing the oil would improve gas mileage per gallon, despite the viscosity of the oil. Have you changed driving habits at all, like hauling more weight, traffic patterns, etc?
What is the difference in mileage now as compared to before?

The shidter should fit as long as it is the same transmissions.

Hope this helps -
aloha
calvin