Not another oil discussion but just a thought:

- We should feel very safe changing oil at 3000 mile (dino oil) with 4-5 quart sump (any other car)
- In my car, it holds 8.5 quarts
- a little calculation say
3000x8.5/4 = 6375 or
3000x8.5/5 = 5100 miles
- so it should be safe with oil change interval of 5000-6000 miles even if I only use dino oil?
- I drive about 20000 miles a year and am changing oil every 5000 miles anyway so about 4 oil change per year. My mechanic charges $70 for synthetic and $30 for dyno. Now that's about $160 saving per year - I know it's not going to break me, I am just trying to justify spending it. My questions are:

1. Does using synthetic actually overkill if I change oil at 5000 mile anyway?
2. Is it really safe for an 98 E-320 engine (FSS) using dino oil (but only use it for 5000 miles)?

Thanks in advance,
JeffreyP