Unless you are going into LA for a reason, I would avoid going straight down I-5. Personally, I would cut over to 99 and across 58 towards Barstow. Before getting to Barstow, you will come to Kramer Junction(intersection of hwy 58 and hwy 395). Go south on 395 to reach I-15. South on I-15, break off to the 215 south, then south to I-10. It saves a bunch of distance/time/and hassle. Its also a major trucking route, so ther are filling stations all along there. I hate to say this, but try to avoid Mojave for fueling. The station on the north end of town is known(locally) for having BAD fuel. Its called Oasis. The PennySavers truck stop is okay(I guess, I always fuel at the CFN station).