Will this oil be ok to use in a 5.4L Triton F150 thru the winter in Houston TX ??? My concern is the 15w on the colder days. The Chevron web site says they make a Delo 400 10w30, but I have not been able to find it anywhere? This would be a great HDO for year round use. The only other option I have considered is the Shell Rotella T 5w40, but your talking a bit more money in comparison to the Chevron Delo 400 15w40.