Millions of pounds will be borrowed to buy dozens of new council vehicles.
But a report says the council can only afford to replace 56 of those in the next couple of years.
Councillors have now approved plans to borrow £2.58m to buy the vehicles.
The cash strapped council has been phasing the purchasing of new vehicles to reduce the impact on its budgets.
In 2014 it said more than half of its roughly 800-strong fleet were beyond their “useful economic life”.
It has bought 199 new vehicles over the past two years but says a quarter of the fleet still needs urgently replacing.
A report says an old fleet increases the risk of higher-costing repairs and breakdowns.
And it says older vehicles are more polluting and can cost three times more to run.
Figures calculated by officials indicate it will cost £291,000 in interest payments to borrow the £2.58m over a ten year period.
Vehicles bought over the past two years include: 90 vans, 11 gritters each costing more than £100,000, nine 4x4 pick-up trucks (£17k each), one vehicle to paint white lines (£116K), a street lighting replacement wagon (£133K), and six new bin wagons, the most expensive of which cost over £150,000.