Earlier this month Ibought a 2004 S40 with ~74k. I just found out that the last oil change - in October, about 1800 miles ago - was done with conventional oil. I was planning to get an Amsoil change on Friday, but now Ihave to takea short road triptomorrow (~300 miles roundtrip). Am I taking too big a risk by not changing the oil immediately? I have an extended warranty, but I can just see them saying, "Oh, sorry, but you once used conventional oil and so the warranty is void." Your advice is greatly appreciated!

 

If you have time and $$$ I would do.. ( I did when I bought mine). This theme is very polemical but for Turbo cars Synthetic oil is important not to cause sludge...

 

The 2004 V40 came from the factory with Castrol 5W-30 conventional oil. Volvo has since changed their recommendation to Castrol 5W-30 semi-synthetic. Using conventional oil in your 2004 S40 will not void your extended warranty. As long as you have receipts showing the oil has been changed as recommended (every 7,500 miles) you'll be fine.

 

The owners manual in my 07 2.4i says something like "castrol 5w-30 recommended, synthetic is only used at owners request for an additional charge." I have only had to change mine once so far and I used Valvoline synpower full synthetic.

To answer your question I would not worry if you check the oil level is good and it looks clean.