I use 20/50 Redline and I just changed it at 6K mileage (2 years of driving). Other than being black, the
oil was in excellent shape. No grit, no sludge.
If cost of
synthetic oil is a problem for you, why do you have a Cobra????? Trade it in on a nice Prius.
![laughing](images/smilies/laughing.gif)
or a 74 Vega
![Whacked](images/smilies/freak6.gif)