Need suggestions for lump sum investment

I have around 8 lakhs in my bank account, and I was thinking of buying a car worth around 15 lakhs after 6-7 months. I have a few SIPs that I've been investing in for a long time, and I was thinking of investing this money for the next 6–7 months in these SIPs. So should I buy some kind of dip instead of keeping the money in the bank? Even after short term capital tax, I could get more returns than if I kept it in the bank. Am I thinking this right, or am I missing something? Any other suggestions?